Control Valve Apparatus

ABSTRACT

In a hydraulic system equipped with a main flow passage for feeding oil to each of lubricated engine parts and a branch passage branched from the main flow passage, a control valve apparatus is provided for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point. The control valve apparatus is configured to control openings of a large flow control section and a small flow control section, depending on a position of a valve element, and further configured to close the opening of the small flow control section, at least in a specified state where the opening of the large flow control section is fully opened with a maximum opening area.

TECHNICAL FIELD

The present invention relates to a control valve apparatus configured tocontrol fluid flow (lubricating and/or working oil flow).

BACKGROUND ART

It is generally known that, in a hydraulic system with a main fluid-flowpassage for feeding oil (lubricating oil) to moving parts of an internalcombustion engine requiring lubrication and a branch passage branchedfrom the main flow passage for feeding oil (working oil) to a hydraulicactuator, a control valve apparatus is disposed in the main flow passagedownstream of a branched point of the branch passage from the main flowpassage, for controlling a flow rate of oil flowing through the mainflow passage downstream of the branched point. One such control valveapparatus has been disclosed in Japanese Patent Provisional PublicationNo. 57-173513 (hereinafter is referred to as “JP57-173513”),corresponding to U.S. Pat. No. 4,452,188, issued on Jun. 5, 1984. In thecontrol valve apparatus (the oil-feed control apparatus) disclosed inJP57-173513, when the flow rate of oil fed into the main flow passage islimited, the flow rate of oil flowing through the main flow passagedownstream of the branched point is limited to an amount of oil passingthrough a bypass passage (an orifice) by means of the control valveapparatus. As a result of this, oil can be preferentially fed into thebranch passage, thereby enhancing the responsiveness of a hydraulicactuator, to which oil (working oil) is delivered by way of the branchpassage.

SUMMARY OF THE INVENTION

However, in the case of the apparatus as disclosed in JP57-173513, thereis a risk of the insufficient flow-rate adjustment.

It is, therefore, in view of the previously-described disadvantages ofthe prior art, an object of the invention to provide a control valveapparatus capable of enhancing a function of flow-rate adjustment.

In order to accomplish the aforementioned and other objects of thepresent invention, in a hydraulic system equipped with a main flowpassage for feeding oil, discharged from an oil pump driven by aninternal combustion engine, to each of lubricated engine parts, a branchpassage branched from the main flow passage at a branched point, and ahydraulic actuator operated by a hydraulic pressure in the branchpassage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowingthrough a portion of the main flow passage downstream of the branchedpoint,

the control valve apparatus configured to control an opening of a largeflow control section and an opening of a small flow control sectionwhose opening area is less than that of the large flow control section,depending on a position of a valve element disposed in the portion ofthe main flow passage downstream of the branched point, and

the control valve apparatus further configured to close the opening ofthe small flow control section, at least in a specified state where theopening of the large flow control section is fully opened with a maximumopening area.

According to another aspect of the invention, in a hydraulic systemequipped with a main flow passage for feeding oil, discharged from anoil pump driven by an internal combustion engine, to each of lubricatedengine parts, a branch passage branched from the main flow passage at abranched point, and a hydraulic actuator operated by a hydraulicpressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowingthrough a portion of the main flow passage downstream of the branchedpoint,

the control valve apparatus comprising a sliding-contact bore into whichan inlet of the main flow passage opens and from which an outlet of themain flow passage opens, and a spool installed to axially move in thesliding-contact bore only as needed, the sliding-contact bore and thespool both disposed in the portion of the main flow passage downstreamof the branched point, and the spool has a first communication passageintercommunicating the inlet and the outlet and a second communicationpassage intercommunicating the inlet and the outlet and having anopening area less than an opening area of the first communicationpassage,

the control valve apparatus configured to bring the first communicationpassage to a communicated state and simultaneously to bring the secondcommunication passage to a non-communicated state, in a first statewhere the spool has moved with a maximum displacement in one axialdirection of the spool, and

the control valve apparatus further configured to bring the secondcommunication passage to a communicated state and simultaneously tobring the first communication passage to a non-communicated state, in asecond state where the spool has moved with a maximum displacement inthe opposite axial direction of the spool.

According to a further aspect of the invention, in a hydraulic systemequipped with a main flow passage for feeding oil, discharged from anoil pump driven by an internal combustion engine, to each of lubricatedengine parts, a branch passage branched from the main flow passage at abranched point, and a hydraulic actuator operated by a hydraulicpressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowingthrough a portion of the main flow passage downstream of the branchedpoint,

the control valve apparatus comprising a sliding-contact bore into whichan inlet of the main flow passage opens and from which an outlet of themain flow passage opens, and a spool installed to axially move in thesliding-contact bore selectively between two opposite axial positionsonly as needed, the sliding-contact bore and the spool both disposed inthe portion of the main flow passage downstream of the branched point,and the spool has a first communication passage intercommunicating theinlet and the outlet and a second communication passageintercommunicating the inlet and the outlet and having an opening arealess than an opening area of the first communication passage,

the control valve apparatus configured to bring the first communicationpassage to a communicated state and simultaneously to bring the secondcommunication passage to a non-communicated state, in a first statewhere the spool has moved to one of the two opposite axial positions,and

the control valve apparatus further configured to bring the secondcommunication passage to a communicated state and simultaneously tobring the first communication passage to a non-communicated state, in asecond state where the spool has moved to the opposite axial position.

The other objects and features of this invention will become understoodfrom the following description with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic system diagram illustrating a hydraulic systemconfiguration of the embodiment, including a main fluid-flow passage, abranch passage, a hydraulic actuator such as a variable valve timingcontrol (VTC) device (cross-sectioned along the line I-I of FIG. 2), anda control valve apparatus.

FIG. 2 is a front elevation view illustrating the VTC deviceincorporated in the hydraulic system of the embodiment and kept at itsmaximum phase-retard position.

FIG. 3 is a front elevation view illustrating the VTC deviceincorporated in the hydraulic system of the embodiment and kept at itsmaximum phase-advance position.

FIG. 4 is a partial cross-section of the control valve apparatus of theembodiment, whose spool is controlled to a large flow-rate side.

FIG. 5 is a partial cross-section of the control valve apparatus of theembodiment, whose spool is controlled to a small flow-rate side.

FIG. 6 is a partial cross-section of a control valve apparatus of asecond comparative example, whose spool is controlled to a smallflow-rate side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, particularly to FIG. 1, a control valveapparatus 1 of the embodiment can be applied to a hydraulic system of aninternal combustion engine of an automotive vehicle.

As can be seen from the hydraulic system configuration of FIG. 1, thehydraulic system is comprised of a hydraulically-operated variable valvetiming control (VTC) device for variably controlling engine valve timing(valve open timing and/or valve closure timing), moving engine partsrequiring lubrication (hereinafter is referred to as “lubricated engineparts”), and an oil supply-and-exhaust mechanism 5 for supplying andexhausting pressure oil (lubricating/working oil) to and from each oflubricated engine parts and the VTC device. The upper-rightcross-section of FIG. 1 shows the partial cross-section taken along theline I-I of FIG. 2, passing through the rotation axis “O” of the VTCdevice of the intake valve side.

The VTC device is a hydraulically-operated phase-converter thatcontinuously varies a relative angular phase of a camshaft 65 to acrankshaft of the engine, by hydraulic pressure of working oil fed tothe VTC device. The VTC device includes a sprocket 91 driven by thecrankshaft via a timing chain and configured to be relatively rotatablewith respect to the camshaft 65, and a phase-change mechanism installedbetween sprocket 91 and camshaft 65 to change a relative angular phaseof camshaft 65 to sprocket 91 (the crankshaft). The VTC device is ahydraulic actuator, which is hydraulically operated by supplying andexhausting working oil to and from the phase-change mechanism via theoil supply-and-exhaust mechanism 5.

The phase-change mechanism includes a phase-converter housing HSG (ahousing member) and a vane member 6 accommodated in the housing HSG. Aplurality of working oil chambers (exactly, phase-advance chambersA1-A4, which are collectively referred to as “phase-advance chamber A”,and phase-retard chambers R1-R4, which are collectively referred to as“phase-retard chamber R”,) are defined by vanes 61-64 and housing HSG. Achange in working oil pressure, acting on each of the vanes, takes placeby the oil supply or oil exhaust to or from the working oil chambers. Asa result, vane member 6 (the camshaft side) is relatively rotated withrespect to housing HSG (the crankshaft side) by a given angle. Underthis condition, torque transmission between them is made. In thismanner, a phase of rotation of camshaft 65 to a phase of rotation of thecrankshaft can be changed.

Oil supply-and-exhaust mechanism 5 is configured to hydraulicallyoperate the VTC device by adjusting the working oil supply-and-exhaustto and from the phase-change mechanism. That is, a volume change in eachof the plurality of working oil chambers occurs by selectively supplyingworking oil to either phase-advance chambers A1-A4 or phase-retardchambers R1-R4 or by selectively exhausting working oil from eitherphase-advance chambers A1-A4 or phase-retard chambers R1-R4 by means ofoil supply-and-exhaust mechanism 5, with the result that vane member 6can be relatively rotated with respect to housing HSG by a predeterminedangle in a normal-directional direction or in a reverse-rotationaldirection. The working oil supply and exhaust, achieved through the oilsupply-and-exhaust mechanism 5, is controlled by control means(concretely, a central processing unit) incorporated in an electroniccontrol unit CU (hereinafter referred to as “controller”).

Oil supply-and-exhaust mechanism 5 includes an oil pump P (serving as ahydraulic pressure source), fluid-flow passages (oil passages) andvarious valves.

Oil pump P (hereinafter referred to as “pump”) is driven by powertransmitted from the engine crankshaft, for discharging engine oil(hereinafter referred to as “oil”). For instance, a variabledisplacement single-direction vane pump that allows for only onedirection of pump rotation, can be used as the pump P. It will beappreciated that pump P is not limited to such a rotary type vane pump.In lieu thereof, a gear-type oil pump, such as an external gear pump oran internal gear pump, may be used.

As the oil passages, oil supply-and-exhaust mechanism 5 includes aninlet passage 52, a supply passage 53 for feeding oil to each oflubricated engine parts, a supply passage 54 for feeding oil to the VTCdevice, and an exhaust passage 57 for exhausting (draining) oil from theVTC device.

As the various valves, oil supply-and-exhaust mechanism includes thecontrol valve apparatus 1, a pressure relief valve 58, and a directionalcontrol valve 59. Inlet passage 52 is configured to interconnect aninlet of pump P and an oil pan O/P detachably installed as a lower partof an engine block EB. Supply passage 53 is configured to interconnectan outlet of pump P and each of lubricated engine parts.

Pump P draws oil from the oil pan O/P via the inlet passage 52 duringoperation (during rotation), and then discharges (feeds) a pressurizedhigh-pressure oil to the supply passage 53. That is, pump P is providedto force-feed oil in the oil pan O/P to the supply passage 53.

Assume that, regarding an oil flow line, the side of pump P, whichsupplies oil, is called “upstream side”, and the opposite side, to whichoil is supplied, is called “downstream side”.

Supply line 53 is a main fluid-flow passage to which oil discharged frompump P is introduced and which is configured to feed the oil to each oflubricated engine parts.

An oil filter O/F is disposed in the supply passage 53 to remove anyimpurities from the oil discharged from pump P.

One end of a bypass passage 55 is connected to a midpoint of the portionof supply passage 53 between oil filter O/F and pump P, whereas theother end of bypass passage 55 is connected to the inlet passage 52.Relief valve 58 is disposed in the bypass passage 55. Relief valve 58 isa normally-closed valve, which is automatically opened when a pressureof the oil, discharged from pump P into supply passage 53, exceeds aspecified limit (a set pressure of relief valve 58), to relieve the oilfrom the supply passage 53 back to the oil pan O/P, thereby preventingthe pressure in supply passage 53 (the internal pressure of thehydraulic system) from increasing beyond the specified value.

Supply passage 54 for oil supply to the VTC device is branched from abranched point 530 of supply passage 53 at the downstream side of oilfilter O/F. In other words, supply passage 53, extending from pump P, isbranched into an oil supply line for lubricating-oil supply to each oflubricated engine parts and an oil supply line (i.e., supply passage 54)for working/lubricating oil supply to the VTC device.

Control valve apparatus 1 is disposed in the supply passage 53downstream of the branched point 530. The portion of supply passage 53,extending from control valve apparatus 1 toward the upstream side, ishereinafter represented as “supply passage 53 a”, whereas the portion ofsupply passage 53, extending from control valve apparatus 1 toward thedownstream side, is hereinafter represented as “supply passage 53 b”.

The upstream supply passage 53 a communicates the outlet of pump P. Thatis, the upstream supply passage 53 a serves as a pump-flow introductoryportion.

The downstream supply passage 53 b is connected to the upstream supplypassage 53 a and also connected to a main oil gallery formed in theengine. In lieu thereof, the downstream supply passage 53 b in itselfmay be a main oil gallery. That is, the downstream supply passage 53 bserves as a lubricating oil passage for feeding the oil in the upstreamsupply passage 53 a to each of lubricated engine parts. Supply passage54 is a branch passage, which is branched from the supply passage 53 afor feeding the oil in supply passage 53 a to the VTC device. Controlvalve apparatus 1 is provided to adjust or control a flow rate of oilflowing through the supply passage 53 downstream of the branched point530, in other words, a flow rate of oil flowing through the downstreamsupply passage 53 b.

The downstream end of supply passage 54 is connected to the directionalcontrol valve 59. Directional control valve 59 is connected to the VTCdevice through a dual hydraulic-circuit system, namely, a phase-retardpassage 50 provided for working/lubricating oil supply-and-exhaust toand from each of phase-retard chambers R1-R4, and a phase-advancepassage 51 provided for working/lubricating oil supply-and-exhaust toand from each of phase-advance chambers A1-A4. Additionally, anoil-exhaust passage (simply, a drain passage) 57 is connected to thedirectional control valve 59. The downstream end of drain passage 57communicates the oil pan O/P.

Directional control valve 59 is a direct-operated electromagneticsolenoid valve (a four-port three-position spring-offset directionalcontrol valve) that is configured to control switching betweenfluid-communication of supply passage 54 and phase-retard passage 50 andfluid-communication of supply passage 54 and phase-advance passage 51,and simultaneously to control switching between fluid-communication ofexhaust passage 57 and phase-advance passage 51 and fluid-communicationof exhaust passage 57 and phase-retard passage 50.

Directional control valve 59 is comprised of a valve body fixedlyconnected to a cylinder head of the engine, a solenoid SOL fixedlyinstalled on the valve body, and a spool (a valve element) slidablyaccommodated in the valve body. The valve body has four ports formedtherein, that is, a supply port 590 communicating the supply passage 54,a first port 591 communicating the phase-retard passage 50, a secondport 592 communicating the phase-advance passage 51, and an exhaust port593 communicating the exhaust passage 57

Solenoid SQL is connected to controller CU via a harness, so as to shift(move) the spool, when solenoid SQL is energized. Under a de-energizedstate of solenoid SQL, by the spring force of a return spring RS, thespool is forced (biased) to its original position (a spring offsetposition) at which fluid-communication between supply port 590 (supplypassage 54) and first port 591 (phase-retard passage 50) is establishedand fluid-communication between second port 592 (phase-advance passage51) and exhaust port 593 (exhaust passage 57) is established. Converselyunder an energized state of solenoid SOL, responsively to a controlcurrent from controller CU, the spool can be moved against the springforce of return spring RS apart from the spring-offset position, andthen held at its fully-energized position at which fluid-communicationbetween supply port 590 (supply passage 54) and second port 592(phase-advance passage 51) is established and fluid-communicationbetween first port 591 (phase-retard passage 50) and exhaust port 593(exhaust passage 57) is established, or held at a given intermediateposition within its entire stroke range. With the spool held at thegiven intermediate position, first and second ports 591 and 592 are bothclosed.

Controller CU (the electronic control unit) generally comprises amicrocomputer. Controller CU includes an input/output interface (I/O),memories (RAM, ROM), and a microprocessor or a central processing unit(CPU). The input/output interface (I/O) of controller CU receives inputinformation from various engine/vehicle sensors, namely, a crank anglesensor (a crankshaft position sensor), an airflow meter (an airflowsensor), a throttle opening sensor (a throttle position sensor), and anengine temperature sensor (such as an engine coolant temperaturesensor). The crank angle sensor is provided for detecting engine speed,and the airflow meter is provided for detecting a quantity of intakeair. Within controller CU, the central processing unit (CPU) allows theaccess by the I/O interface of input informational data signals from thepreviously-discussed engine/vehicle sensors. For instance, on the basisof sensor signals from the engine/vehicle sensors, the more recentengine operating condition can be detected.

Controller CU is also configured to output a pulse control current,which is determined depending on the detected engine operatingcondition, to the solenoid SOL of directional control valve 59, tochange the path of flow through the directional control valve (in otherwords, to carry out flow-path switching control among fluid-flowpassages 50, 51, 54, and 57), thus enabling oil to be selectivelysupplied to either phase-advance chambers A1-A4 or phase-retard chambersR1-R4 or enabling oil to be selectively exhausted from eitherphase-advance chambers A1-A4 or phase-retard chambers R1-R4. In thismanner, a working pressure for the VTC device can be controlled.

Controller CU is further configured to output a control current, whichis determined depending on the detected engine operating condition, to asolenoid 34 of a pilot valve 3 (described later) of control valveapparatus 1, to carry out switching control (fluid-flow restrictingcontrol) between fluid-flow passages 53 and 54, thus enabling moreimproved fine control of flow for a flow rate of oil, which is fed toeach of lubricated engine parts and/or the VTC device.

The construction of the intake-valve side VTC device incorporated in thehydraulic system of the embodiment is hereinafter described in referenceto FIGS. 1-3.

Assuming that the direction of the rotation axis “O” of the VTC device,that is, the direction of the rotation axis of the intake-port camshaft(camshaft 65) is taken as an “X-axis”, a direction of the “X-axis”,directed from the camshaft to the side of installation of the VTC deviceon the camshaft end, is a positive X-axis direction, whereas theopposite direction of “X-axis” is a negative X-axis direction.

FIGS. 2-3 are front elevation views (as viewed from the positive X-axisdirection) illustrating the internal construction of the VTC deviceincorporated in the hydraulic system of the embodiment, but with a frontplate 8 removed. In other words, each of FIGS. 2-3 is apartially-assembled view that a housing body 10 of housing HSG and vanemember 6 are assembled and installed on a rear plate 9 of housing HSG.In FIGS. 1 to 3, oil passages formed in the vane member 6, are indicatedby the broken line. In the shown embodiment, control valve apparatus 1can be used for oil-flow control for working oil to be fed to theintake-valve side VTC device. Control valve apparatus 1 may be used foroil-flow control for working oil to be fed to the exhaust-valve side VTCdevice.

The VTC device is installed on the axial end 65 a of camshaft 65, facingin the positive X-axis direction, by means of one cam bolt 66. Cam bolt66 has a head 660 and a shank 661 consisting of an unthreaded shankportion and a male-screw-threaded portion.

Camshaft end 65 a is formed therein with a bolt hole 650 into which themale-screw-threaded portion of shank 661 is screwed. Bolt hole 650 isformed to axially extend from the end face 653 of camshaft end 65 a,facing in the positive X-axis direction, to a predetermined depth in thenegative X-axis direction. Bolt hole 650 is constructed by alarge-diameter cylindrical bore portion 651 and a small-diametercylindrical bore portion 652, both bored in the camshaft end 65 a inthat order from the end face 653. The inner periphery of small-diametercylindrical bore portion 652 is formed with a female-screw-threadedportion into which the male-screw-threaded portion of shank 661 of cambolt 66 is screwed. Camshaft end 65 a has a disk-shaped flanged portion654 formed at a specified position corresponding to an axial distancemeasured from the end face 653 in the negative X-axis direction.

The VTC device (the VTC unit) includes the housing HSG, vane member 6,and an oil-passage structural member 5 a. Housing HSG is laid out at thecamshaft end 65 a. Housing HSG has a timing sprocket 91 (a firstsprocket described later) formed integral therewith. Sprocket 91 has adriven connection with the crankshaft so that torque is transmitted fromthe crankshaft to the timing sprocket. Vane member 6 is fixedlyconnected to the camshaft end 65 a by means of cam bolt 66. Vane member6 is accommodated in the housing HSG, so that relative rotation of vanemember 6 to housing HSG is permitted. Oil-passage structural member 5 ais a substantially cylindrical block in which a portion of phase-retardpassage 50 and a portion of phase-advance passage 51 are formed.

Housing HSG includes front plate 8, rear plate 9, and housing body 10.

Housing body 10 is formed as a cylindrical hollow housing member, openedat both ends in the opposite X-axis directions. Housing body 10 is madeof sintered alloy materials, such as iron-based sintered alloymaterials. Housing body 10 is integrally formed on its inner peripherywith a plurality of radially-inward protruded shoes 11, 12, 13, and 14.Concretely, the four shoes 11-14 are spaced from each other byapproximately 90 degrees in the direction around the rotation axis “O”(that is, in the circumferential direction). As seen in FIG. 2, each ofshoes 11-14 is formed as a radially-inward protruded partition wallportion extending in the X-axis direction of housing HSG. Each of shoes11-14 has a substantially trapezoidal shape in lateral cross section,taken in the direction perpendicular to the X-axis direction, andtapered radially inwards. As viewed in the X-axis direction, both sidefaces of each of shoes 11-14, facing in the circumferential direction,are formed as substantially flat surfaces configured to be conformableto straight lines extending radially (i.e., in the radial direction ofhousing body 10) outwards from the rotation axis “O”. As viewed from thepositive X-axis direction, each of the innermost ends of theradially-inward protruded shoes 11-14, opposing to the rotation axis“O”, are formed as somewhat concave circular-arc end faces, which areconfigured to be substantially conformable to the shape of the outerperiphery of a vane rotor 60 (described later) of vane member 6. As seenin FIG. 2, shoes 11-14 are formed substantially at their centers intrapezoidal lateral cross section with respective bolt insertion holes110, 120, 130, and 140 (through holes extending in the X-axis direction)into which bolts b are inserted. Front plate 8 is fixedly installed onthe left-hand axial end faces (viewing FIG. 1) of shoes 11-14, facing inthe positive X-axis direction, whereas rear plate 9 is fixedly installedon the right-hand axial end faces of shoes 11-14, facing in the negativeX-axis direction. As seen in FIG. 2, the innermost ends of shoes 11-14have respective axially-elongated seal retaining grooves 111, 121, 131,and 141, formed substantially in their centers in the circumferentialdirection and extending in the X-axis direction. Four seal retaininggrooves 111, 121, 131, and 141 are formed into a substantiallyrectangle. Each of seal retaining grooves 111, 121, 131, and 141 isformed over the entire axial length of the associated shoe. Four oilseal members 112, 122, 132, and 142, each having a substantially squarelateral cross section, are fitted into respective seal retaining grooves111, 121, 131, and 141. Additionally, four seal springs, concretely,four leaf springs (not shown), are retained in respective seal retaininggrooves 111, 121, 131, and 141, in a manner so as to force four sealmembers 112, 122, 132, and 142 into abutment (sliding-contact) with theouter peripheral surface of vane rotor 60 over the entire axial lengthin the X-axis direction. During relative rotation of vane rotor 60 tohousing HSG, four seal members 112, 122, 132, and 142 are kept insliding-contact with the outer peripheral surface of vane rotor 60 bythe spring forces of the seal springs. As viewed from the positiveX-axis direction, a substantially rectangular cut-out portion 114 isformed in the innermost end of the side face 113 of the first shoe 11,facing in the clockwise direction.

Front plate 8 is a housing member that hermetically closes the openingend of housing body 10, facing in the positive X-axis direction, inother words, the leftmost ends (viewing FIG. 1) of phase-advance chamberA and phase-retard chamber R, facing in the positive X-axis direction.Front plate 8 is formed into a substantially disk shape by press-workingsteel materials. Front plate 8 has a centrally-bored, large-diameterbolt insertion hole (an axial through hole) 80 into which cam bolt 66and oil-passage structural member 5 a are both inserted duringassembling of the VTC device. Additionally, front plate 8 is formed withcircumferentially equidistant-spaced, four bolt holes (through holesextending in the X-axis direction), which are configured to be opposedto respective bolt insertion holes 110, 120, 130, and 140 of housingbody 10 in the X-axis direction.

Rear plate 9 is a housing member that hermetically closes the openingend of housing body 10, facing in the negative X-axis direction, inother words, the rightmost ends (viewing FIG. 1) of phase-advancechamber A and phase-retard chamber R, facing in the negative X-axisdirection, while permitting a rotor shaft portion 60 b (described later)of vane rotor 60 to be inserted through the central bore of rear plate9. Rear plate 9 is made of sintered alloy materials, such as iron-basedsintered alloy materials. Rear plate 9 includes a plate body 90, andfirst and second sprockets 91 and 92.

Plate body 90 includes a disk-shaped portion (on the side of thepositive X-axis direction) and a cylindrical portion (on the side of thenegative X-axis direction). Plate body 90 is formed with a centralstepped bore 93 arranged coaxially with the rotation axis “O”. Steppedbore 93 serves as a rotor supporting bore into which the rotor shaft 60b of vane rotor 60 (vane member 6) is inserted so that rotor shaft 60 bis rotatably supported. Concretely, stepped bore 93 is comprised of amain supporting portion (a bearing bore portion) 93 a and a rightmostopening end portion 93 b (the rightmost end of the negative X-axisdirection of stepped bore 93, viewing FIG. 1) whose inside diameter isdimensioned to be greater than that of the main supporting portion 93 a.

The inside diameter of main supporting portion 93 a of stepped bore 93is dimensioned to be slightly greater than the outside diameter of rotorshaft 60 b.

The inside diameter of rightmost opening end portion 93 b of steppedbore 93 is dimensioned to be greater than the outside diameter of theflanged portion 654 of camshaft 65, such that a portion of the flangedportion 654 can be inserted into the rightmost opening end portion 93 b.

Plate body 90 of rear plate 9 is formed with circumferentiallyequidistant-spaced, four bolt holes (female screw-threaded portionsformed in the X-axis direction), which are configured to be opposed torespective bolt insertion holes 110, 120, 130, and 140 of housing body10 in the X-axis direction.

Front plate 8, housing body 10, and rear plate 9 are integrallyconnected to each other by tightening four bolts b. In more detail, eachof four bolts b is inserted into the associated bolt hole of front plate8 and also inserted into the associated bolt insertion hole of housingbody 10 from the positive X-axis direction, and then screwed into theassociated female-screw-threaded portion of rear plate 9. In thismanner, front plate 8 and rear plate 9 are fixedly connected to housingbody 10.

The disk-shaped portion (the side of the positive X-axis direction) ofplate body 90 is integrally formed on its outer periphery with the firstsprocket 91. The cylindrical portion (the side of the negative X-axisdirection) of plate body 90 is integrally formed on its outer peripherywith the second sprocket 92.

The outer periphery of first sprocket 91 is formed integral with atoothed portion in meshed-engagement with a first timing chain. In asimilar manner, the outer periphery of second sprocket 92 is formedintegral with a toothed portion in meshed-engagement with a secondtiming chain. First sprocket 91 is driven clockwise (viewing FIG. 2) bythe crankshaft via the first chain, so that rear plate 9 (housing HSG),integrally formed with first sprocket 91, is rotated in the samerotation direction (i.e., clockwise). Second sprocket 92, together withrear plate 9, is rotated clockwise, so that an exhaust-valve side VTCdevice is driven via the second chain.

As best seen in FIG. 3, a cylindrical bore 900, which is closed at oneaxial end and has a predetermined depth in the X-axis direction, isformed at a position of plate body 90 adjacent to the side face of thefirst shoe 11, facing clockwise.

Vane member 6 serves as a driven rotational member that is rotatablerelative to housing HSG. That is, vane member 6, together with camshaft65, rotates clockwise (viewing FIG. 2). Vane member 6 is comprised offour radially-extending vane blades 61-64 that receive working oilpressure, and vane rotor 60. Vane rotor 60 has an axially-extendingcentral bore 602 (described later) into which cam bolt (vane mountingbolt) 66 is inserted for bolting vane rotor 60 to the camshaft end 65 aby axially tightening the cam bolt. The axis of vane rotor 60 iscoaxially aligned with the axis of camshaft 65.

Rotor 60 is formed into a substantially cylindrical shape, and comprisedof a rotor body 60 a and a rotor shaft 60 b both coaxially aligned witheach other. Rotor body 60 a and four vane blades 61-64 are integrallyformed with each other. Rotor shaft 60 b is integrally formed with therotor body 60 a in such a manner as to extend from the rotor body 60 ain the negative X-axis direction.

The outside diameter of rotor body 60 a is dimensioned to be slightlygreater than the inside diameter of main supporting portion 93 a ofstepped bore 93 of rear plate 9 and the inside diameter of boltinsertion hole 80 of front plate 8. The outside diameter of rotor shaft60 b is dimensioned to be slightly less than the inside diameter of mainsupporting portion 93 a of stepped bore 93 of rear plate 9.

Rotor 60 has a substantially cylindrical bore 600, extending coaxiallywith the rotation axis “O”, and opening in the positive X-axis directionand closed at the opposite side. The entire axial length of cylindricalbore 600 is dimensioned to reach a predetermined depth of rotor shaft 60b in the negative X-axis direction. Cylindrical bore 600 is an oil-pathconfiguration bore into which oil-passage structural member 5 a of theVTC device is inserted and installed. The left-hand side opening end(viewing FIG. 1) of cylindrical bore 600 is machined as a taperedportion (a beveled or chamfered portion) 604.

Also, rotor 60 has a substantially cylindrical bore 601, extendingcoaxially with the rotation axis “O”, and opening in the negative X-axisdirection and closed at the opposite side. The entire axial length ofcylindrical bore 601 is dimensioned to reach a predetermined depth ofrotor shaft 60 b in the positive X-axis direction. Cylindrical bore 601is a camshaft insertion bore into which camshaft end 65 a is insertedand installed. The axial length of cylindrical bore 601 is dimensionedto be slightly greater than the distance from the end face 655 ofcamshaft flanged portion 654, facing in the positive X-axis direction,to the end face 653 of camshaft end 65 a, facing in the positive X-axisdirection. Central bore 602 (a through hole through the rotation axis“O”) is formed in the partition wall through which cylindrical bores600-601 are divided. Central bore 602 serves as a cam-bolt insertionhole into which cam bolt 66 is inserted.

The head 660 of cam bolt 66 is positioned in cylindrical bore 600,whereas the shank 661 of cam bolt 66 is inserted through central bore602 into the bolt hole 650 of camshaft 65. Then, the male-screw-threadedportion of shank 661 of cam bolt 66 is screwed into thefemale-screw-threaded portion of cylindrical bore portion 652 of bolthole 650. In this manner, rotor 60 is integrally connected to thecamshaft end 65 a by tightening the cam bolt 66. At this time, the endface 603 of rotor 60, facing in the negative X-axis direction, isbrought into abutted-engagement with the end face 655 of camshaftflanged portion 654, facing in the positive X-axis direction.

Rotor 60 is rotatably supported on the housing HSG, while being kept insliding-contact with each of oil seal members 112, 122, 132, and 142,which are fitted into respective seal retaining grooves 111, 121, 131,and 141 the innermost ends of four shoes 11-14.

Rotor 60 has radially-outward protruded, circumferentially-equidistantspaced four vane blades 61-64 formed on its outer periphery.

Four blades 61-64 are formed integral with rotor body 60 a. The axiallength of each of blades 61-64, measured in the X-axis direction, isdimensioned to be approximately equal to that of rotor body 60 a. Withvane member 6 installed in the housing HSG, the axial end face of eachof blades 61-64, facing in the positive X-axis direction, and the axialend face of front plate 8, facing in the negative X-axis direction, areopposed to each other by a very small clearance space. In a similarmanner, the axial end face of each of blades 61-64, facing in thenegative X-axis direction, and the axial end face of rear plate 9 (platebody 9 a), facing in the positive X-axis direction, are opposed to eachother by a very small clearance space.

As best seen in FIG. 2, in the hydraulically-operated four-blade vanemember equipped VTC device, the areas of the outside circumferences offour blades 61-64 of the four-blade vane member 6, in other words, thecircumferential widths of four blades 61-64 are dimensioned to besomewhat different from each other. Four blades 61-64 are classifiedinto two sorts, namely a maximum-width blade (that is, the first blade61) and the remaining narrow-width blades 62-64. The remainingnarrow-width blades 62-64 have almost the same circumferential width andthe same radial length. Three narrow-width blades 62-64 are configuredto be substantially rectangular in lateral cross section. As viewed inthe X-axis direction, rounded corners of both side faces of the root ofeach of narrow-width vane blades 62-64 are further recessed. The firstblade 61 is formed as a maximum-width blade whose circumferential widthis dimensioned to be greater than that of each of three narrow-widthblades 62-64, so as to be able to accommodate a lock mechanism(described later) in the first blade 61. The first blade 61 isconfigured to have an inverted trapezoidal shape in lateral crosssection.

Four blades 61-64 have respective axially-elongated seal retaininggrooves 611, 621, 631, and 641, formed in their outermost ends (apexes)and extending in the X-axis direction. Each of four seal retaininggrooves 611, 621, 631, and 641 is formed into a substantially rectangle,as viewed in the X-axis direction. Four oil seal members (four apexseals) 612, 622, 632, and 642, each having a substantially squarelateral cross section, are fitted into respective seal retaining grooves611, 621, 631, and 641. Additionally, four seal springs, concretely,four leaf springs (not shown), are retained in respective seal retaininggrooves 611, 621, 631, and 641, in a manner so as to force four sealmembers 612, 622, 632, and 642 into abutment (sliding-contact) with theinner peripheral surface of housing body 10.

As seen in FIG. 2, the first blade 61 has a cylindrical bore 70 formedas a through hole extending in the X-axis direction. The bore 70 servesas a lock-piston sliding-motion permitting bore (simply, a lock-pistonbore) in which a retractable lock piston (described later) of a lockmechanism 7 is slidably installed. Lock-piston bore 70 is comprised of asmall-diameter chamber 701 formed on the side of the negative X-axisdirection and a large-diameter chamber 702 formed on the side of thepositive X-axis direction.

The anticlockwise edge of the outermost end of the first blade 61 isformed as a rounded edge having a circular-arc curved surface, whosecenter is identical to the center of lock-piston bore 70, and which hasa radius of curvature greater than the radius of lock-piston bore 70 andis configured to be curved along the circumference of lock-piston bore70. The circular-arc curved surface of the rounded edge is formed to becontinuous with the side face 613 of the first blade 61.

A radial groove 605 is formed in the axial end face of the first blade61, facing in the positive X-axis direction. Radial groove 605 is acut-out groove interconnecting the opening end of the positive X-axisdirection of lock-piston bore 70 and the opening end of the positiveX-axis direction of cylindrical bore 600 of rotor 60.

As viewed in the X-axis direction, four oil chambers are defined by fourpairs of two adjacent shoes (11, 12; 12, 13; 13, 14; 14, 11). Each ofthe four oil chambers is divided into phase-advance chamber A andphase-retard chamber R by the blade disposed between the two adjacentshoes. For instance, the first phase-advance chamber A1 is definedbetween the side face 113 of the first shoe 11, facing in the clockwisedirection, and the side face 613 of the first blade 61, facing in theanticlockwise direction, whereas the first phase-retard chamber R1 isdefined between the side face 614 of the first blade 61, facing in theclockwise direction, and the side face 123 of the second shoe 12, facingin the anticlockwise direction. Phase-advance chamber A and phase-retardchamber R are partitioned from each other in a fluid-tight fashion witha less oil leakage by means of oil seal members 112, 122, 132, and 142.

As viewed from the positive X-axis direction, when vane member 6 rotatesanticlockwise relative to housing HSG by a predetermined angle or more,the side face 113 of the first shoe 11, facing in the clockwisedirection, and the side face 613 of the first blade 61, facing in theanticlockwise direction, are brought into wall-contact with each other(see FIG. 2). With the first-shoe side face 113 and the first-blade sideface 613 kept in wall-contact with each other, there is a slightaperture between two opposed side walls of shoe 12 and blade 62, thereis a slight aperture between two opposed side walls of shoe 13 and blade63, and there is a slight aperture between two opposed side walls ofshoe 14 and blade 64. The maximum rotary motion of vane member 6relative to housing HSG in the anticlockwise direction (i.e., in thephase-retard direction), can be restricted by abutment between the sideface 113 of the first shoe 11 and the side face 613 of the first blade61. That is, the side face 113 of the first shoe 11 and the side face613 of the first blade 61 cooperate with each other to provide a firststopper (an anticlockwise rotary-motion stopper for vane member 6).

Conversely when vane member 6 rotates clockwise relative to housing HSGfrom the maximum phase-retard position of vane member 6 shown in FIG. 2,the side face 123 of the second shoe 12, facing in the anticlockwisedirection, and the side face 614 of the first blade 61, facing in theclockwise direction, are brought into wall-contact with each other (seeFIG. 3). With the second-shoe side face 123 and the first-blade sideface 614 kept in wall-contact with each other, there is a slightaperture between two opposed side walls of shoe 13 and blade 62, thereis a slight aperture between two opposed side walls of shoe 14 and blade63, and there is a slight aperture between two opposed side walls ofshoe 11 and blade 64. The maximum rotary motion of vane member 6relative to housing HSG in the clockwise direction (i.e., in thephase-advance direction), can be restricted by abutment between the sideface 123 of the second shoe 12 and the side face 614 of the first blade61. That is, the side face 123 of the second shoe 12 and the side face614 of the first blade 61 cooperate with each other to provide a secondstopper (a clockwise rotary-motion stopper for vane member 6).

As discussed above, the maximum anticlockwise rotary motion of vanemember 6 relative to housing HSG and the maximum clockwise rotary motionof vane member 6 relative to housing HSG are restricted by means of thefirst stopper (113, 613) and the second stopper (123, 614).

As can be seen in FIGS. 2-3 shoes 11-14 of housing body 10 and blades61-64 of vane member 6 are configured so that, over the entire range ofrelative rotation of vane member 6 to housing HSG, the volume ofphase-retard chamber R and the volume of phase-advance chamber A can beboth kept at a value greater than “0”, and thus the opening area of aphase-retard oil passage (e.g., a phase-retard oil passage 501 describedlater), opening into phase-retard chamber R, and the opening area of aphase-advance oil passage (e.g., a phase-advance oil passage 511described later), opening into phase-advance chamber A, can be ensured.For instance, as seen in FIG. 2, the volume of the first phase-advancechamber A1 and the opening area of the phase-advance oil passage 511 areensured by a space, defined by the cut-out portion 114 of the first shoe11. For instance, as seen in FIG. 3, the volume of the firstphase-retard chamber R1 and the opening area of the phase-retard oilpassage 501 are ensured by an aperture, formed by the difference ofradius of curvature between the anticlockwise rounded edge of theinnermost end of the second shoe 12 and the clockwise rounded corner ofthe root of the first blade 61.

A portion of phase-retard passage 50 and a portion of phase-advancepassage 51 are formed in each of oil-passage structural member 5 a andvane member 6.

Axial passages 50 a and 51 a, extending in the X-axis direction, areopened at the end face of the negative X-axis direction of oil-passagestructural member 5 a. The opening end (the rightmost axial end, viewingFIG. 1) of axial passage 51 a is hermetically closed by a press-fit ballB1. An internal space 50 b is defined between the end face of thenegative X-axis direction of oil-passage structural member 5 a and theinner peripheral surface of cylindrical bore 600. A groove 51 c is anannular circumferential groove formed in the outer peripheral surface ofoil-passage structural member 5 a at a predetermined axial positionsomewhat spaced apart from the end face of the negative X-axis directionof oil-passage structural member 5 a. A radial passage 51 b is formed inoil-passage structural member 5 a in a manner so as to intercommunicateaxial passage 51 a and groove 51 c. Axial passage 50 a and space 50 bconstruct a portion of phase-retard passage 50, whereas axial passage 51a, radial passage 51 b, and groove 51 c construct a portion ofphase-advance passage 51.

Oil-passage structural member 5 a has three circumferential groovesformed in its outer peripheral surface. Oil seals S1-S3 are fitted intothe respective circumferential grooves. Oil-passage structural member 5a is installed in cylindrical bore 600 of rotor 60, so that relativerotation of oil-passage structural member 5 a to vane member 6 ispermitted. The outer peripheral surface of each of oil seals S1-S3 iskept in sliding-contact with the inner peripheral surface of cylindricalbore 600. Oil seals S1-S2 are laid out in a manner so as to sandwich thegroove 51 c between them, thus ensuring a high fluid-tightness ofphase-advance passage 51. Oil seal S3 is laid out near the end face ofthe negative X-axis direction of oil-passage structural member 5 a toensure a high fluid-tightness of phase-retard passage 50 (in particular,space 50 b).

Rotor 60 has radial oil holes 501-504 and radial oil holes 511-514formed therein. Oil holes 501-504 and 511-514 are radially-extendingthrough holes formed in rotor body 60 a. These oil holesintercommunicate the inner peripheral surface of cylindrical bore 600and the outer peripheral surface of rotor body 60 a. Oil holes 501-504construct a portion of phase-retard passage 50, whereas oil holes511-514 construct a portion of phase-advance passage 51.

As viewed from the positive X-axis direction, oil holes 501-504 are laidout adjacent to the respective clockwise sides of the roots of thefirst, second, third, and fourth blades 61-64 (see FIG. 2). The axialpositions of oil holes 501-504 are placed near the axial end of thenegative X-axis direction of rotor body 60 a (see FIG. 1).

As viewed from the positive X-axis direction, oil holes 511-514 are laidout adjacent to the respective anticlockwise sides of the roots of thefirst, second, third, and fourth blades 61-64 (see FIG. 2). The axialpositions of oil holes 511-514 are placed to be slightly offset from themidpoint of rotor body 60 a toward the positive X-axis direction (seeFIG. 1).

In a state where oil-passage structural member 5 a is inserted andinstalled into cylindrical bore 600 of rotor 60, the inside opening endsof phase-retard side radial oil holes 501-504 are placed in the negativeX-axis direction from the oil seal S3 and open into the space 50 b. Onthe other hand, the outside opening ends of phase-retard side radial oilholes 501-504 open into respective phase-retard chambers R1-R4. Theinside opening ends of phase-advance side radial oil holes 511-514 aresandwiched between oil seals S1-S2, and opposed to and open into thegroove 51 c. The outside opening ends of phase-advance side radial oilholes 511-514 open into respective phase-advance chambers A1-A4.

Phase-retard passage 50, extending from directional control valve 59, iscommunicated with each of phase-retard chambers R1-R4 through axialpassage 50 a of oil-passage structural member 5 a (a non-rotary member),space 50 b, and radial oil holes 501-504 of vane member 6 (a rotarymember).

Phase-advance passage 51, extending from directional control valve 59,is communicated with each of phase-advance chambers A1-A4 through axialpassage 51 a of oil-passage structural member 5 a, radial passage 51 b,groove 51 c, and radial oil holes 511-514 of vane member 6.

Lock mechanism 7 is disposed between vane member 6 (exactly, the firstblade 61) and rear plate 9 of housing HSG, for disabling rotary motionof vane member 6 relative to rear plate 9 by locking and engaging vanemember 6 with housing HSG, and for enabling rotary motion of vane member6 relative to rear plate 9 by unlocking (or disengaging) vane member 6from housing HSG. The VTC device is configured in a manner so as to belocked by the lock mechanism 7 at the maximum phase-retard position atwhich rotary motion of vane member 6 relative to housing HSG isrestricted by the first stopper (113, 613).

Lock mechanism 7 is comprised of a retractable lock piston 71, aconcavity 730 of rear plate 9, and an engaging-and-disengagingmechanism. The engaging-and-disengaging mechanism operates to engage thelock piston 71 with the concavity 730 via an extension stroke of lockpiston 71, depending on an engine operating condition. Theengaging-and-disengaging mechanism also operates to disengage the lockpiston 71 from the concavity 730 via a retraction stroke of lock piston71, depending on an engine operating condition.

Lock piston 71 is an iron taper-pin-shaped engaging member, which isformed into a substantially cylindrical hollow shape and closed at oneaxial end. Lock piston 71 is slidably installed in the lock-piston bore70 of the first blade 61, so that lock piston 71 can reciprocate orslide in the X-axis direction.

Lock piston 71 is comprised of a cylindrical sliding portion 710accommodated in the lock-piston bore 70 so that a sliding motion ofsliding portion 710 relative to lock-piston bore 70 is permitted, and atapered head portion 714 going in and out of the lock-piston bore 70.Sliding portion 710 is comprised of a small-diameter portion 711 formedon the side of the negative X-axis direction and a large-diameterportion 712 formed on the side of the positive X-axis direction.Small-diameter portion 711 is formed into a substantially cylindricalhollow shape and closed at one axial end, and opened in the positiveX-axis direction. Small-diameter portion 711 is slidably installed insmall-diameter chamber 701 of lock-piston bore 70. The substantiallycircular-truncated-cone-shaped (frusta-conical), tapered head portion714 is integrally formed on the side of the negative X-axis direction ofthe bottom (the right-hand closed end, viewing FIG. 1) 713 ofsmall-diameter portion 711. Head portion 714 has a trapezoidallongitudinal cross-section and has a curved surface (a tapered surface)that the diameter of the circle of the frustum decreases in the negativeX-axis direction from the bottom (the root of head portion 714) to thetop (the tip of head portion 714). Large-diameter portion 712 is a basalportion of lock piston 71, that is, an annular flanged portion formed atthe leftmost end of sliding portion 710 in the positive X-axisdirection. The outside diameter of large-diameter portion 712 isdimensioned to be greater than that of small-diameter portion 711.Large-diameter portion 712 is slidably installed in large-diameterchamber 702 of lock-piston bore 70.

On the other hand, the previously-discussed concavity 730, which isclosed at one axial end, is formed in the end face of rear plate 9,facing in the positive X-axis direction. Concavity 730 is a lock-pistonengaging hole into which the head portion 714 of lock piston 71 can beinserted at the maximum phase-retard position of vane member 6 shown inFIG. 2.

Engaging concavity 730 is constructed by an inner periphery of a sleeve73 (a substantially cylindrical cup-shaped engaging-concavity structuralmember closed at one axial end). Rear plate 9 is formed with anaxially-bored retaining hole 900. That is, sleeve 73 (the cup-shapedengaging-concavity structural member) is press-fitted into the retaininghole 900 of rear plate 9, such that engaging concavity 730 is defined inthe cup-shaped sleeve 73.

Engaging concavity 730 has a substantially trapezoidal axial crosssection, cut along a plane through the axis of the cup-shaped sleeve 73.Engaging concavity 730 is formed as a tapered hole whose inside diametergradually increases toward the opening end of the positive X-axisdirection. In other words, engaging concavity 730 has a curved surfacethat the diameter of the circle of the frustum decreases in the negativeX-axis direction from the opening end of engaging concavity 730 to thebottom face of cup-shaped sleeve 73. The cone angle of the innerperipheral surface engaging concavity 730 is dimensioned to beapproximately identical to that of the outer peripheral surface of headportion 714 of lock piston 71.

When rotary motion of vane member 6 relative to housing HSG in thephase-retard direction occurs and then the maximum rotary motion of vanemember 6 in the phase-retard direction is restricted by the firststopper (113, 613), that is, when the volume of phase-advance chamber A1becomes minimum, as viewed in the X-axis direction, the circumferentialposition of head portion 714 of lock piston 71 becomes identical to thatof engaging concavity 730 of rear plate 9. In other words, thecircumferential position of engaging concavity 730 is determined ordesigned so that, when the head portion 714 of lock piston 71 is broughtinto engagement with the engaging concavity 730 of rear plate 9, theangular position of vane member 6 relative to housing HSG is broughtinto an optimal angular position (i.e., the maximum phase-retardposition) suited to an engine-startup period.

Fully taking account of the slight difference between the slightlytapering diameter of the inner periphery of engaging concavity 730 andthe slightly tapering diameter of the outer periphery of lock-pistonhead portion 714, that is, in order to reliably keep the locked state ofvane member 6 with rear plate 9 (housing HSG) at the maximumphase-retard position, the circumferential position of the axis ofengaging concavity 730 of the rear plate side is designed to be slightlyoffset anticlockwise (viewing FIG. 2) from the axis of lock-piston headportion 714.

A back-pressure chamber 72 for lock piston 71 is also defined in thelock-piston bore 70. Back-pressure chamber 72 is a low-pressure chamberpartitioned by lock piston 71 to face in the positive X-axis directionwith respect to lock piston 71. Concretely, back-pressure chamber 72 isdefined by the axial end face (the inside face) of front plate 8, facingin the negative X-axis direction, the inner peripheral surface oflock-piston bore 70, and the inner peripheral surface of cylindricalsliding portion 710 of lock piston 71.

The engaging-and-disengaging mechanism is comprised of a coiledcompression spring 74, serving as an engaging (locking) biasing member,and a communication hole 75 and a communication groove 76, both servingas disengaging (unlocking) oil passages.

A spring retainer 74 a is disposed in the back-pressure chamber 72. Thebasal portion (the head portion) of the positive X-axis direction ofspring retainer 74 a is kept in sliding-contact with the inside face offront plate 8, whereas the axially-protruding portion of the negativeX-axis direction of spring retainer 74 a is loosely fitted into theinner periphery of coil spring 74.

Coil spring 74 is disposed in back-pressure chamber 72 under preload.The left-hand axial end of coil spring 74, facing in the positive X-axisdirection, is kept in abutted-engagement with the left-hand annular endof the head portion of spring retainer 74 a, facing in the negativeX-axis direction. The right-hand axial end of coil spring 74, facing inthe negative X-axis direction, is kept in abutted-engagement with thebottom (the right-hand closed end, viewing FIG. 1) 713 of small-diametersliding portion 711 of lock piston 71. Coil spring 74 is a spring-biasmember that permanently forces the lock piston 71 in the negative X-axisdirection, that is, toward the engaging concavity 730 of rear plate 9.

Also defined in the lock-spring bore 70 are two pressure-receivingchambers, each of which produces a hydraulic pressure acting on the lockpiston 71. The first pressure-receiving chamber 77 is defined in thelarge-diameter chamber 702 of lock-piston bore 70 by the annular endface of small-diameter chamber 701 of lock-piston bore 70, facing in thepositive X-axis direction, the annular end face of large-diameterportion 712 of lock piston 71, facing in the negative X-axis direction,the outer peripheral surface of small-diameter sliding portion 711, andthe inner peripheral surface of large-diameter chamber 702 oflock-piston bore 70. The second pressure-receiving chamber 78 is definedby the outer peripheral surface of the tapered head portion 714, facingin the negative X-axis direction, and the inner peripheral surface ofcup-shaped sleeve 73, facing in the positive X-axis direction.

The first blade 61 is formed with oil passages therein, for introducinghydraulic pressure in the working oil chamber (phase-retard chamber R orphase-advance chamber A) into either the first pressure-receivingchamber 77 or the second pressure-receiving chamber 78. Concretely, thefirst blade 61 is formed with the circumferentially-extendingcommunication hole 75 through which the first phase-retard chamber R1and the first pressure-receiving chamber 77 are always intercommunicatedto introduce hydraulic pressure in the first phase-retard chamber R1into the first pressure-receiving chamber 77. In a similar manner, thefirst blade 61 is also formed with the circumferentially-extendingcommunication groove 76 through which the first phase-advance chamber A1and the second pressure-receiving chamber 78 are alwaysintercommunicated to introduce hydraulic pressure in the firstphase-advance chamber A1 into the second pressure-receiving chamber 78(into the engaging concavity 730 in the locked state of vane member 6).By the way, even at the maximum phase-retard position, the opening areaof the communication groove 76 opening into the first phase-advancechamber A1 is ensured by the space, defined by the cut-out portion 114of the first shoe 11.

A part of working oil, supplied to the first phase-retard chamber R1,and then introduced through the communication hole 75 into the firstpressure-receiving chamber 77, produces a hydraulic pressure that forceslock piston 71 in its retracting direction (i.e., in the positive X-axisdirection). In the same manner, a part of working oil, supplied to thefirst phase-advance chamber A1, and then introduced through thecommunication groove 76 into the second pressure-receiving chamber 78,also produces a hydraulic pressure that forces lock piston 71 in itsretracting direction (i.e., in the positive X-axis direction).

At the maximum phase-retard position of vane member 6, with an extendingstroke of the head portion 714 of lock piston 71 out of the first blade61 (the lock-piston bore 70) by the spring force of coil spring 74, thehead portion 714 is inserted into and engaged with the engagingconcavity 730. With lock piston 71 engaged with the engaging concavity730, relative rotation between rear plate 9 and vane member 6, that is,relative rotation between housing HSG and camshaft 65 is restricted(disabled).

On the other hand, the large-diameter portion 712 of lock piston 71 isforced in the positive X-axis direction by hydraulic pressure of workingoil fed from the first phase-retard chamber R1 through the communicationhole 75 to the first pressure-receiving chamber 77. Additionally, thetapered head portion 714 of lock piston 71 is forced in the positiveX-axis direction by hydraulic pressure of working oil fed from the firstphase-advance chamber A1 through the communication groove 76 to thesecond pressure-receiving chamber 78. As a result, the tapered headportion 714 of lock piston 71 goes out of the engaging concavity 730,and then lock piston 71 retracts into the lock-piston bore 70 of thefirst blade 61, and thus lock piston 71 becomes disengaged from theengaging cavity 730 of rear plate 9. Back-pressure chamber 72communicates with the bolt insertion hole 80 of front plate 8 throughthe radial groove 605. Thus, hack-pressure chamber 72 is opened to theexterior space of the VTC device (i.e., to the atmosphere), in otherwords, to a low-pressure space (see FIG. 1).

The operation of the VTC device including the VTC control system ishereunder described in detail.

In an engine stopped state, pump P is kept inoperative, and thus oilsupply to the working oil chambers (phase-advance chamber A andphase-retard chamber R) is also stopped. Additionally, there is noapplication of control current (exciting current) from controller CU tothe solenoid SOL of directional control valve 59, and thusfluid-communication of supply passage 54 and phase-retard passage 50 andfluid-communication of phase-advance passage 51 and exhaust passage 57are established.

Just before the engine has been stopped, owing to the alternating torqueacting on the camshaft 65, vane member 6 becomes held at its initialposition, i.e., the maximum phase-retard position (see FIG. 2). Also, atthis maximum phase-retard position, the lock piston 71 of lock mechanism7 is kept in engagement with the engaging concavity 730 of rear plate 9,so that relative rotation of vane member 6 to housing HSG is restricted.

Thereafter, when the engine is cranked and started by turning theignition key ON, the pump P begins to operate. Just after the engine hasbeen started, oil supply to the VTC device (i.e., a working oilpressure) becomes still insufficient. At this time, by virtue of lockmechanism 7, vane member 6 is restricted or held at its initial position(the maximum phase-retard position suited to an engine startup, i.e., asmooth cranking operation). As a result of this, it is possible toenhance an engine startability, while avoiding undesirablecollision-contact (noise) between vane member 6 (concretely, the sideface 613 of the first blade 61) and housing HSG (concretely, the sideface 113 of the first shoe 11 of housing body 10), which may occur owingto the alternating torque.

When the engine has been started but any control current has not yetbeen inputted from controller CU to the solenoid SOL of directionalcontrol valve 59, fluid-communication of supply passage 54 andphase-retard passage 50 and fluid-communication of phase-advance passage51 and exhaust passage 57 remain established. Under these conditions,oil, fed from pump P to supply passage 54, is delivered to each ofphase-retard chambers R1-R4.

As previously described, a part of working oil in the first phase-retardchamber R1 is introduced through communication hole 75 of lock mechanism7 into the first pressure-receiving chamber 77. The hydraulic pressureof working oil, introduced into the first pressure-receiving chamber 77,serves to force lock piston 71 in its retracting direction (i.e., in thepositive X-axis direction). As soon as the hydraulic pressure in thefirst phase-retard chamber R1, in other words, the hydraulic pressure insupply passage 54, becomes greater than or equal to a specified pressurevalue, the head portion 714 of lock piston 71 becomes completelydisengaged from the engaging concavity 730 of rear plate 9. As, aresult, the locked state of vane member 6 becomes released, so thatrelative rotation of vane member 6 to housing HSG becomes permitted andan arbitrary change in engine valve timing (valve open timing and/orvalve closure timing) becomes enabled. After a transition of vane member6 to its unlocked state has occurred, during operation of the engine atlow speeds, vane member 6 is still maintained at its maximumphase-retard position by a comparatively low working oil pressuresupplied to each of phase-retard chambers R1-R4.

Thereafter, suppose that the engine operating condition shifts to amiddle speed range, and thus the spool of directional control valve 59shifts to the fully-energized position, responsively to a pulse controlcurrent having a given duty ratio from controller CU.Fluid-communication between supply passage 54 and phase-advance passage51 and fluid-communication between phase-retard passage 50 and exhaustpassage 57 are established. As a result, oil in each of phase-retardchambers R1-R4 is exhausted and then returned to oil pan O/P, whereasoil, fed from pump P to supply passage 54, is delivered to each ofphase-advance chambers A1-A4.

Owing to a rise in hydraulic pressure in each of phase-advance chambersA1-A4, vane member 6 begins to rotate apart from the maximumphase-retard position, so that rotary motion of vane member 6 relativeto housing HSG in the clockwise direction (i.e., in the phase-advancedirection) occurs. Under these conditions, the hydraulic pressure in thefirst pressure-receiving chamber 77 of lock mechanism 7 tends to fall,but a part of working oil, supplied to the first phase-advance chamberA1, is introduced through the communication groove 76 into the secondpressure-receiving chamber 78 of lock mechanism 7. The working oil,introduced into the second pressure-receiving chamber 78, produces ahydraulic pressure that forces lock piston 71 in its retractingdirection (i.e., in the positive X-axis direction). Thus, the unlockedstate, in which the head portion 714 of lock piston 71 is completelydisengaged from the engaging concavity 730 of rear plate 9, can bemaintained.

A relative angular phase of camshaft 65 to the crankshaft becomeschanged to the phase-advance side, so that intake-valve open timing(IVO) and intake-valve closure timing (IVC) can be both phase-advanced.As a result, a valve overlap period, during which the open periods ofintake and exhaust valves are overlapped, tends to increase, thusenhancing a combustion efficiency.

Thereafter, suppose that due to a further engine speed rise the engineoperating condition shifts to a high speed range, and thus the spool ofdirectional control valve 59 is continuously kept at the fully-energizedposition, responsively to a pulse control current having a given dutyratio from controller CU. High-pressure working oil can be continuouslysupplied to each of phase-advance chambers A1-A4. As a result, a furtherclockwise rotational motion of vane member 6 relative to housing HSGoccurs, and thus a relative angular phase of camshaft 65 to thecrankshaft is further phase-advanced. Finally, the relative angularphase of vane member 6 reaches its maximum phase-advance position atwhich the volume of each of phase-advance chambers A1-A4 becomes maximum(see FIG. 3). As a result, a valve overlap period, during which the openperiods of intake and exhaust valves are overlapped, becomes maximum.

After this, suppose that, owing to an engine speed fall, the hydraulicpressure in each of phase-advance chambers A1-A4 tends to gradually falland thus a relative angular phase of camshaft 65 to the crankshaft isreturned back to the phase-retard side. Thus, the previously-discussedvalve overlap period becomes small. At this time, the hydraulic pressurein supply passage 54, remains kept at a pressure level above thespecified pressure value, and hence the unlocked state, in which thehead portion 714 is completely disengaged from the engaging concavity730, remains maintained.

The construction of control valve apparatus 1 is hereunder described indetail in reference to FIGS. 4-5. The cross-section of each of FIGS. 4-5shows the partial cross-section passing through the centerline “Q” ofcontrol valve apparatus 1 of the embodiment (that is, the axis ofsliding motion of a spool 20 described later in detail and constructinga part of control valve apparatus 1). The centerline “Q” of controlvalve apparatus 1 is hereinafter referred to as “axis Q”.

Assume that the direction, perpendicular to one side face 100 of engineblock EB, is taken as an “x-axis”, the direction, parallel to the sideface 100 of engine block EB, is taken as a “y-axis”, a direction of the“x-axis”, directed apart from engine block EB is a positive x-axisdirection, and a direction of the “y-axis”, facing apart from the supplypassage 53 a with respect to an annular groove 561, is a positive y-axisdirection.

First of all, the oil-path configuration of the side of engine block BB,on which control valve apparatus 1 is installed, is described.

Supply passage 53 (that is, the upstream supply passage 53 a and thedownstream supply passage 53 b) and supply passage 54 are formed in theengine block EB by machining (concretely, drilling). The upstream supplypassage 53 a is formed to extend approximately straight in the y-axisdirection, while being spaced from the end face 100 of engine block EBby a predetermined distance. The end of the negative y-axis direction ofsupply passage 53 a is connected to the outlet of pump P. Supply passage54 for working/lubricating oil supply to the VTC device is branched fromthe branched point 530 of the positive y-axis direction of supplypassage 53 a. The supply passage 54 is hereinafter referred to as“branch passage 54”. Branch passage 54 is formed to extend approximatelystraight in the x-axis direction. The end of the negative x-axisdirection of branch passage 54 is connected to directional control valve59. The downstream supply passage 53 b is formed to extend approximatelystraight in the x-axis direction. The downstream supply passage 53 b isconnected, on the side of the negative x-axis direction, to each oflubricated engine parts. The end of the positive y-axis direction ofsupply passage 53 a and the end of the positive x-axis direction ofsupply passage 53 b are connected to each other in a unit mountingportion 56 formed in the engine block EB.

Unit mounting portion 56 is a mounting hole drilled in the engine blockEB for mounting a valve unit including the control valve apparatus 1.Unit mounting portion 56 is comprised of a housing retaining bore 560,an annular groove 561, and a seal retaining bore 562. Seal retainingbore 562, annular groove 561, and housing retaining bore 560 aresubstantially cylindrical bores formed inside of the side face 100 ofengine block EB, and aligned substantially coaxially with the downstreamsupply passage 53 b with respect to the axis “Q”. Seal retaining bore562, annular groove 561, and housing retaining bore 560 are laid out inthat order, in the negative x-axis direction. Regarding the insidediameters of seal retaining bore 562, annular groove 561, and housingretaining bore 560, the inside diameter of seal retaining bore 562 isdimensioned to be greater than that of annular groove 561, and theinside diameter of annular groove 561 is dimensioned to be greater thanthat of housing retaining bore 560. That is, unit mounting portion 56 isformed as a two-stepped bore. Regarding the dimensions of seal retainingbore 562, annular groove 561, and housing retaining bore 560, measuredin the x-axis direction, the seal retaining bore 562 is dimensioned tobe shorter than the annular groove 561, and the annular groove 561 isdimensioned to be shorter than the housing retaining bore 560. Annulargroove 561 is connected, on the side of the negative y-axis direction,to the supply passage 53 a. The width of annular groove 561, measured inthe x-axis direction, is dimensioned to be greater than the insidediameter of supply passage 53 a. The end of the positive y-axisdirection of supply passage 53 a opens from the inner peripheral surfaceof annular groove 561 into the internal space. Supply passage 53 b isconnected to the end of the negative x-axis direction of housingretaining bore 560. The inside diameter of housing retaining bore 560 isdimensioned to be greater than that of supply passage 53 b. The end ofthe positive x-axis direction of supply passage 53 b opens at the end ofnegative x-axis direction of housing retaining bore 560. Seal retainingbore 562 opens from the side face 100 of engine block EB.

Component parts of control valve apparatus 1 are hereunder described indetail.

Control valve apparatus 1 is comprised of a spool valve 2 (serving as aflow-path selector) and a pilot valve 3 (provided for a pilotoperation), both accommodated in a single housing (the same valvecasing) 4 common to these two valves 2-3. As a valve unit with both thespool valve 2 and the pilot valve 3, control valve apparatus 1 isinstalled in the unit mounting portion 56 of engine block EB. Controlvalve apparatus 1 is configured to produce a control hydraulic pressureby the electromagnetically-operated pilot valve 3. Spool valve 2 isoperated (opened or closed) by the control hydraulic pressure. That is,as the control valve apparatus 1, a pilot-operated type is adopted.

Spool valve 2 has a spool (a main valve element) 20. Spool valve 2 is adirectional control valve configured to change the path of flow throughthe valve element (i.e., with a sliding motion of spool 20). The spoolvalve 2 functions as a two-way valve that performs switching action ofthe path of flow by opening and closing action of the valve element(spool 20), and also functions as a flow control valve that controls aflow rate of oil through the valve element by a flow-constrictingorifice action. Pilot valve 3 is a control valve configured to operatethe spool valve 2 (the main valve) by a pilot pressure.

Housing 4 is a support member serving to support or mount both spoolvalve 2 and pilot valve 3. Housing 4 is installed on the unit mountingportion 56. Housing 4 is made of aluminum alloy materials bydie-casting. Housing 4 is comprised of a spool valve body (a spool valvehousing) 4 a, a flanged portion 4 b, and a pilot valve body (a pilotvalve housing) 4 c, all formed integral with each other.

Spool valve body 4 a of housing 4 has a back-pressure portion 41 formedon the side of the positive x-axis direction and a flow-passage portion42 formed on the side of the negative x-axis direction. The innerperiphery of spool valve body 4 a is formed as a substantiallycylindrical-hollow sliding-contact bore 40 that serves as a guidesurface designed to ensure a smooth sliding motion of spool 20.

Back-pressure portion 41 is formed into a substantially cylindricalshape. The end of the positive x-axis direction of back-pressure portion41 is formed as an opening end. The end of the negative x-axis directionof back-pressure portion 41 is formed to be continuous with theflow-passage portion 42. The inner peripheral surface of back-pressureportion 41 has a female-screw-threaded portion 410 formed on the side ofpositive x-axis direction. The inner peripheral surface of back-pressureportion 41 is formed as a large-diameter bore 40 a (a large-diameterportion of sliding-contact bore 40 for spool 20). The end of thepositive x-axis direction of large-diameter bore 40 a has an annulargroove 411 (see FIG. 5) formed in the inner periphery of bore 40 a inclose proximity to the end of the negative x-axis direction offemale-screw-threaded portion 410.

The end of the negative x-axis direction of back-pressure portion 41 isintegrally formed with the flanged portion 4 b radially-outwardextending along the plane perpendicular to the axis “Q” and located inclose proximity to the flow-passage portion 42.

Flanged portion 4 b has a bolt hole 43 formed as a through holeextending in the x-axis direction. A mounting bolt is inserted into thebolt hole 43 from the side of the positive x-axis direction. By screwingand tightening the mounting bolt into a female-screw-threaded portionformed in the side face 100 of engine block EB, housing 4 is fixedlyconnected to and mounted on the engine block EB. An O ring (an oil sealmember) S4 is fitted into the seal retaining bore 562 of engine blockEB. Under a state where housing 4 has been bolted to the side face 100of engine block EB, O ring S4 is sandwiched and compressed between theend face of the negative x-axis direction of flanged portion 4 b ofhousing 4 and the end face of the positive x-axis direction of sealretaining bore 562, thus ensuring a high fluid-tightness of the interiorspace of unit mounting portion 56.

Back-pressure portion 41 has an oblique hole 412 formed on the side ofthe positive y-axis direction and the negative x-axis direction. Obliquehole 412 is formed as a substantially-straight through hole penetratingthe inner and outer peripheries of back-pressure portion 41. Obliquehole 412 is opened to the exterior space of engine block EB through theouter peripheral surface of back-pressure portion 41 on the side of thepositive x-axis direction of flanged portion 4 b. Oblique hole 412 isalso opened to the interior space of sliding-contact bore 40 through theinner peripheral surface of large-diameter bore 40 a (a large-diameterportion of sliding-contact bore 40 for spool 20) at a given position,somewhat overlapping with the flanged portion 4 b in close proximity tothe end of the negative x-axis direction of back-pressure portion 41.Oblique hole 412, intercommunicating the interior and exterior spaces ofback-pressure portion 41 (spool valve body 4 a), serves as an airbreather that functions to facilitate a change in volume of the internalspace defined between the outer periphery of spool 20 and the innerperiphery of large-diameter bore 40 a of sliding-contact bore 40.

A threaded plug 413 is screwed into the female-screw-threaded portion410 of back-pressure portion 41, so as to hermetically close the openingend of back-pressure portion 41, facing in the positive x-axisdirection. That is, the side of the backface of spool 20 is closed in afluid-tight fashion by the threaded plug 413.

Flow-passage portion 42 of spool valve body 4 a is formed into asubstantially cylindrical bore closed at one end and having a diametersmaller than a diameter of back-pressure portion 41. Flow-passageportion 42 is formed with communication holes (for example,communication holes (through holes) 421 and 423).

The inner peripheral surface of flow-passage portion 42 is formed as asmall-diameter bore 40 b (a small-diameter portion of sliding-contactbore 40 for spool 20). The inside diameter of small-diameter bore 40 bis dimensioned to be less than that of large-diameter bore 40 a. The endof the positive x-axis direction of small-diameter bore 40 b and the endface of the negative x-axis direction of flanged portion 4 b are alignedwith each other in the x-axis direction, in a manner so as to form astepped annular portion in cooperation with large-diameter portion 40 a.The outside diameter of the outer peripheral surface of flow-passageportion 42 is dimensioned to be approximately equal to that oflarge-diameter bore 40 a. The outer peripheral surface of the left-handhalf (viewing FIGS. 4-5) of flow-passage portion 42 is formed to becontinuous with the end face of the negative x-axis direction of flangedportion 4 b, while drawing a moderately curved surface.

The end of the negative x-axis direction of flow-passage portion 42 isinserted and fitted into the housing retaining bore 560. As a result,sliding-contact bore 40 (large-diameter bore 40 a and small-diameterbore 40 b) and annular groove 561 are accurately positioned and alignedcoaxially with each other with respect to the axis “Q”. By way of suchan accurate positioning and fitting process, it is possible to suppressan undesirable fluid-communication between annular groove 561 andhousing retaining bore 560 via the outer peripheral aide of flow-passageportion 42.

A plurality of circumferentially-equidistant spaced circular holes (fourholes 421-424 in the shown embodiment) are formed in the basal end ofthe positive x-axis direction of flow-passage portion 42. Each of holes421-424 is formed as a through hole radially penetrating the inner andouter peripheries of flow-passage portion 42. Each of through holes421-424 is a communication hole that opens from the outer peripheralsurface of flow-passage portion 42 and also opens from the innerperipheral surface of sliding-contact bore 40 (especially,small-diameter bore 40 b). In the shown embodiment, althoughflow-passage portion 42 has four circular through holes 421-424, it willbe appreciated that the number of through holes is not limited to “4”.The shape and the number of through holes may be modified.

The diameters of through holes 421-424 are dimensioned to beapproximately equal to each other, and also dimensioned to be less thanthe diameter of supply passage 53 a. The openings (i.e., through holes421-424) of housing 4, installed in unit mounting portion 56, arelocated at the inner peripheral side of annular groove 561. In otherwords, annular groove 561 is located at the outer peripheral side of theopenings (i.e., through holes 421-424) of housing 4. The axial positionof the center of the x-axis direction of each of through holes 421-424is laid out to be approximately identical to the position of the x-axisdirection of the centerline of supply passage 53 a. Of four throughholes 421-424, the first through hole 421 is located to open in thenegative y-axis direction, in a manner so as to be opposed to the supplypassage 53 a in the y-axis direction.

The end (a bottom 425) of the negative x-axis direction of flow-passageportion 42 is formed with a hole 420. Hole 420 is formed as a throughhole penetrating the inner and outer peripheries of the bottom 425 andextending in the x-axis direction and aligned substantially coaxiallywith the axis “Q”. Hole 420 is a communication hole that opens into theexterior space of flow-passage portion 42 (i.e., the inner peripheralside of housing retaining bore 550) on the side of the negative x-axisdirection of bottom 425 in a manner so as to be opposed to the supplypassage 53 b in the x-axis direction, and also opens into the interiorspace of flow-passage portion 42 (i.e., the inner peripheral side ofsmall-diameter bore 40 b of sliding-contact bore 40) on the side of thepositive x-axis direction of bottom 425. The inside diameter of throughhole 420 is dimensioned to be slightly greater than one-half of theinside diameter of small-diameter bore 40 b of sliding-contact bore 40,and also dimensioned to be less than the inside diameter of supplypassage 53 b.

Pilot valve body 4 c is formed as a substantially cylindrical portionthat extends in the negative y-axis direction from the outer peripheryof back-pressure portion 41 of spool valve body 4 a. Pilot valve body 4c and spool valve body 4 a are formed integral with each other.

Pilot valve body 4 c is a pilot-valve mounting bore for pilot valve 3.Pilot valve body 4 c has a large-diameter bore 440 that opens into theexterior space of housing 4 on the side of the negative y-axisdirection, and a small-diameter bore 441 formed substantially coaxiallywith the large-diameter bore 440 in close proximity to the side of thepositive y-axis direction of large-diameter bore 440. The insidediameter of small-diameter bore 441 is dimensioned to be less than thatof large-diameter bore 440.

Additionally, pilot valve body 4 c has an axial passage 442 and a radialpassage 443 both formed therein, for supplying or exhausting oil (for apilot operation) to or from back-pressure portion 41 of spool valve body4 a. Axial passage 442 is formed to extend in the y-axis direction. Theend of the positive y-axis direction of axial passage 442 opens into thesliding-contact bore 40 of back-pressure portion 41 (i.e., the annulargroove 411 of large-diameter bore 40 a shown in FIG. 5). The end of thenegative y-axis direction of axial passage 442 is connected to a relaypassage 303 of pilot valve 3. Radial passage 443 is formed to extend inthe x-axis direction. The end of the negative x-axis direction of radialpassage 443 opens from the end face of the negative x-axis direction offlanged portion 4 b in a manner so as to communicate the annular groove561 and the seal retaining bore 562 of unit mounting portion 56. The endof the positive x-axis direction of radial passage 443 opens into theend of the positive y-axis direction of small-diameter bore 441 in amanner so as to be connected to the axial passage 442 through the relaypassages 302-303.

Pilot valve 3 has an oil passage 30, a ball 31, a spring 32, an armature33, and a solenoid 34.

Oil passage 30 is constructed by an axial passage 301, and relaypassages 302-305. Axial passage 301 is formed to extend in the y-axisdirection. The end of the positive y-axis direction of axial passage 301communicates the radial passage 443 of pilot valve body 4 c of housing4, whereas the end of the negative y-axis direction of axial passage 301communicates the relay passage 302. Relay passage 302 is formed toextend in the y-axis direction. The end of the negative y-axis directionof relay passage 302 communicates the relay passage 303. Relay passage303 is formed to extend in the direction perpendicular to the y-axis.The end of the positive y-axis direction of relay passage 303communicates the axial passage 442 of pilot valve body 4 c of housing 4,whereas the end of the negative y-axis direction of relay passage 303communicates the relay passage 304. Relay passage 304 is formed toextend in the y-axis direction. The side of the negative y-axisdirection of relay passage 304 communicates the relay passage 305. Relaypassage 305 is connected through an exhaust passage (not shown) to theoil pan O/P, and thus opened to the atmosphere.

Ball 31 is installed on the side of the negative y-axis direction ofaxial passage 301. Ball 31 is permanently biased in the negative y-axisdirection by means of the spring 32 installed in the axial passage 301in a manner so as to close the opening of relay passage 302. Armature 33has a needle-shaped pointed portion that extends in the y-axis directionin a manner so as to penetrate all of relay passages 302-304. The end ofthe positive y-axis direction of the needle-shaped pointed portion ofarmature 33 is installed to be kept in abutment with the ball 31. Asealing surface is provided at the end of the negative y-axis directionof armature 33, that is, the root of the needle-shaped pointed portionof armature 33. By bringing the sealing surface of armature 33 intoabutted-engagement with a sealing surface formed in the opening of thenegative y-axis direction of relay passage 304, fluid-communicationbetween two relay passages 304 and 305 can be blocked. Solenoid 34 isconnected via a connector 35 to an electric power source. When solenoid34 is energized, the electric coil of solenoid 34 creates a magneticforce that forces armature 33 in the positive y-axis direction.

Spool 20 is a piston slidably accommodated in sliding-contact bore 40 ofspool valve body 4 a. Spool 20 is made of iron-based metal materials,and formed into a substantially cylindrical shape by cold forging. Spool20 is partitioned into a back-pressure portion 21 defined on the side ofthe positive x-axis direction and a flow-passage portion 22 defined onthe side of the negative x-axis direction by a partition wall portion23.

Back-pressure portion 21 is formed into a substantially cylindricalhollow shape, but closed at one axial end. The end of the positivex-axis direction of back-pressure portion 21 is formed as an openingend. The end of the negative x-axis direction of back-pressure portion21 is closed by the partition wall portion 23. In other words, the innerperipheral side of back-pressure portion 21 is formed as a recessedportion, concretely, a substantially cylindrical bore 210 whose bottom(closed end) is the partition wall portion 23 (see FIG. 4).

The end of the positive x-axis direction of back-pressure portion 21,that is, the perimeter of the left-hand side opening (viewing FIGS. 4-5)of back-pressure portion 21 is formed integral with a flanged portion211. Flanged portion 211 is formed as a large-diameter annularring-shaped flange radially-outward extending from the outer peripheralsurface of spool 20 and having an outside diameter greater than theoutside diameter of the other cylindrical portion of spool 20. Thedimension (the axial length) of the x-axis direction of flanged portion211 is dimensioned to be greater than that of annular groove 411 ofhousing 4.

The end face of the positive x-axis direction of flanged portion 211 isformed with a groove 214 having a predetermined depth in the x-axisdirection. Groove 214 is a straight radial groove extending in theradial direction of spool 20 in a manner so as to intercommunicate theinner peripheral side (cylindrical bore 210) and the outer peripheralside of flanged portion 211.

The length of back-pressure portion 21 in the x-axis direction, that is,the distance between the end of the positive x-axis direction ofback-pressure portion 21 and the end face of the positive x-axisdirection of partition wall portion 23 is dimensioned to beapproximately equal to the axial length of large-diameter bore 40 a (alarge-diameter portion of sliding-contact bore 40).

The outside diameter of the circumference of flanged portion 211 isdimensioned to be slightly less than the inside diameter oflarge-diameter bore 40 a (a large-diameter portion of sliding-contactbore 40).

Flow-passage portion 22 is formed into a substantially cylindricalhollow shape, but closed at one axial end. The end of the negativex-axis direction of flow-passage portion 22 is formed as an opening end.The end of the positive x-axis direction of flow-passage portion 22 isclosed by the partition wall portion 23. In other words, the innerperipheral side of flow-passage portion 22 is formed as a substantiallycylindrical bore 220 whose bottom (closed end) is the partition wallportion 23 (see FIG. 4).

Flow-passage portion 22 has a first groove 221 and a second groove 222,both formed in the outer periphery of flow-passage portion 22.

The first groove 221 is an annular groove (of a constant width in thex-axis direction) located to be slightly offset from the midpoint offlow-passage portion 22 toward the negative x-axis direction and formedaround the entire circumference of flow-passage portion 22. Thedimension of the first groove 221 (in the x-axis direction) isdimensioned to be slightly less than the diameter of each of throughholes 421-424 of housing 4.

The second groove 222 is an annular groove (of a constant width ofapproximately one-third the width of the first groove 221 in the x-axisdirection) located at the position sandwiched between the first groove221 and the partition wall portion 23 and formed around the entirecircumference of flow-passage portion 22. The distance between the endof the negative x-axis direction of the second groove 222 and the end ofthe negative x-axis direction of spool 20 is dimensioned to beapproximately equal to the distance between the end of the negativex-axis direction of each of through holes 421-424 of housing 4 and theend of the positive x-axis direction of the bottom 425. Also, thedistance between the end of the negative x-axis direction of the secondgroove 222 and the end of the negative x-axis direction of spool 20 isdimensioned to be approximately equal to the distance between the end ofthe positive x-axis direction of each of through holes 421-424 ofhousing 4 and the end of the negative x-axis direction of the threadedplug 413.

The depths of first and second grooves 221 and 222 in the radialdirection of spool 20 are approximately equal to each other.

A plurality of circumferentially-equidistant spaced circular holes (fourholes 223, 224, 225, and 226 in the shown embodiment) are further formedin the grooved portion of flow-passage portion 22 that the first groove221 is formed. Each of holes 223-226 is formed as a through holeradially penetrating the inner and outer peripheries of flow-passageportion 22. Each of holes 223-226 is a communication hole that opensfrom the bottom (the inside groove surface) of the first groove 221 andalso opens from the inner peripheral surface of cylindrical bore 220. Inthe shown embodiment, although flow-passage portion 22 has four throughholes 223-226, it will be appreciated that the number of through holesis not limited to “4”. The shape and the number of through holes may bemodified.

The diameters of through holes 223-226 are dimensioned to beapproximately equal to each other, and also dimensioned to be slightlyless than the dimension of the first groove 221, measured in the x-axisdirection.

A hole 227 is further formed in the grooved portion of flow-passageportion 22 that the second groove 222 is formed. Hole 227 is formed as athrough hole radially penetrating the inner and outer peripheries offlow-passage portion 22. Hole 227 is a communication hole that opensfrom the bottom (the inside groove surface) of second groove 222 andalso opens from the inner peripheral surface of cylindrical bore 220.Hole 227 constructs an orifice. That is, through hole 227 is aflow-constriction orifice that intercommunicates the inner and outerperipheries of flow-passage portion 22 with a flow-constricting action.In the shown embodiment, although flow-passage portion 22 has onethrough hole 227, it will be appreciated that the number of a throughhole is not limited to “1”. The shape and configuration and the numberof a through hole may be modified. For instance, two or more throughholes (i.e., two or more flow-constriction orifices) may be formed toadjust a fluid-flow passage area (i.e., an orifice area) through anorifice constriction.

The diameter of through hole 227 is dimensioned to be less than thedimension of the second groove 222, measured in the x-axis direction,and also dimensioned to be approximately equal to one-fourth of theinside diameter of each of through holes 223-226.

The length of flow-passage portion 22 in the x-axis direction, that is,the distance between the end of the negative x-axis direction offlow-passage portion 22 and the end face of the negative x-axisdirection of partition wall portion 23 is dimensioned to be less thanthe length of flow-passage portion 42 of housing 4 in the x-axisdirection, and also dimensioned to be approximately equal to the lengthof annular groove 561 in the x-axis direction.

The outside diameter of the outer peripheral surface of flow-passageportion 22 is dimensioned to be slightly less than the inside diameterof small-diameter bore 40 b (a small-diameter portion of sliding-contactbore 40).

(Installation State of Spool Valve)

Flanged portion 211 of spool 20 is slidably installed in back-pressureportion 41 of housing 4 so that the outer peripheral surface of flangedportion 211 slides in the x-axis direction with respect to the innerperipheral surface of large-diameter bore 40 a (a large-diameter portionof sliding-contact bore 40). Back-pressure portion 21 and flow-passageportion 22 of spool 20 are slidably installed in housing 4, so that theouter peripheral surface of back-pressure portion 21 and flow-passageportion 22, except for the flanged portion 211 of spool 20, slides inthe x-axis direction with respect to the inner peripheral surface ofsmall-diameter bore 40 b (a small-diameter portion of sliding-contactbore 40).

The first pressure chamber is defined by the inner peripheral surface ofsmall-diameter bore 40 b (a small-diameter portion of sliding-contactbore 40) and all sidewall surfaces of flow-passage portion 22, facing inthe negative x-axis direction, whereas the second pressure chamber(i.e., a back-pressure chamber of spool 20) is defined by the innerperipheral surface of large-diameter bore 40 a (a large-diameter portionof sliding-contact bore 40), the end face of the negative x-axisdirection of threaded plug 413, and all sidewall surfaces ofback-pressure portion 21, facing in the positive x-axis direction.

The first group of sidewall surfaces of flow-passage portion 22, facingin the negative x-axis direction, constructs a first pressure-receivingsurface for receiving a hydraulic pressure (in the first pressurechamber) acting on the spool 20 from the side of the negative x-axisdirection so as to force the spool 20 in the positive x-axis direction.

The second group of sidewall surfaces of back-pressure portion 21,facing in the positive x-axis direction, constructs a secondpressure-receiving surface for receiving a hydraulic pressure (in thesecond pressure chamber) acting on the spool 20 from the side of thepositive x-axis direction so as to force the spool 20 in the negativex-axis direction.

An area D1 of the first pressure-receiving surface is set or formed tobe less than an area D2 of the second pressure-receiving surface by anarea of the sidewall surface of flanged portion 211, facing in thepositive x-axis direction, that is, D1<D2.

An annular space α1 is defined by the first groove 221 between the outerperipheral surface of flow-passage portion 22 and the inner peripheralsurface of small-diameter bore 40 b (a small-diameter portion ofsliding-contact bore 40). In a similar manner, an annular space α2 isdefined by the second groove 222 between the outer peripheral surface offlow-passage portion 22 and the inner peripheral surface ofsmall-diameter bore 40 b. Through holes 223-226, opening at the bottom(the inside groove surface) of the first groove 221, communicate theannular space α1, whereas through hole 227, opening at the bottom (theinside groove surface) of second groove 222, communicates the annularspace a2.

Rotary motion of spool 20 about the axis “Q” with respect to thesliding-contact bore 40 is not restricted. Sliding motion of spool 20 inthe positive x-axis direction is restricted by abutment between the endface of the positive x-axis direction of spool 20 (flanged portion 211)and the end face of the negative x-axis direction of threaded plug 413(see FIG. 4). The restricted position of spool 20 is hereinafterreferred to as “position A”. That is, the end face of the positivex-axis direction of spool 20 (flanged portion 211) and the end face ofthe negative x-axis direction of threaded plug 413 cooperate with eachother to provide a first stopper (a sliding-motion stopper for spool 20in the positive x-axis direction).

Also, sliding motion of spool 20 in the negative x-axis direction isrestricted by abutment between the end face of the negative x-axisdirection of spool 20 (flow-passage portion 22) and the inside face ofbottom 425 of flow-passage portion 42 of housing 4, facing in thepositive x-axis direction (see FIG. 5). The restricted position of spool20 is hereinafter referred to as “opposite position B”. That is, the endface of the negative x-axis direction of spool 20 (flow-passage portion22) and the inside face of bottom 425 of flow-passage portion 42 ofhousing 4, facing in the positive x-axis direction, cooperate with eachother to provide a second stopper (a sliding-motion stopper for spool 20in the negative x-axis direction).

At the position “A” (see FIG. 4), back-pressure portion 21 of spool 20is positioned within the back-pressure portion 41 of housing 4, whereasflow-passage portion 22 is positioned within the flow-passage portion 42of housing 4 in a manner so as to almost accord with the annular groove561 of unit mounting portion 56. As viewed in the radial direction ofhousing 4, at the position “A”, the entire range of the grooved area offlow-passage portion 22, in which first groove 221 is formed, ispositioned to almost accord with the area of flow-passage portion 42 ofhousing 4, in which through holes 421-424 are formed. On the other hand,the second groove 222 is positioned to be slightly offset from the endof the positive x-axis direction of each of through holes 421-424 towardthe positive x-axis direction. The entire range of the grooved area offlow-passage portion 22, in which second groove 222 is formed, ispositioned within the remaining area (i.e., a root 426 of flow-passageportion 42 of housing 4 corresponding to the side of the positive x-axisdirection of flow-passage portion 42), in which through holes 421-424are not formed.

At the position “A” (see FIG. 4), the volume of an annular space βdefined between the outer peripheral surface of back-pressure portion 21(and the end face of the negative x-axis direction of flanged portion211) and the inner peripheral surface of large-diameter bore 40 a (alarge-diameter portion of sliding-contact bore 40) becomes maximum.

At the opposite position “B” (see FIG. 5), most of back-pressure portion21 and flow-passage portion 22 are positioned within the flow-passageportion 42 of housing 4. As viewed in the radial direction of housing 4,at the opposite position “B”, the entire range of the grooved area offlow-passage portion 22, in which the first groove 221 is formed, ispositioned within the remaining area (i.e., a tip of flow-passageportion 42 of housing 4 corresponding to the side of the negative x-axisdirection of flow-passage portion 42), in which through holes 421-424are not formed. On the other hand, the end of the negative x-axisdirection of the second groove 222 and the end of the negative x-axisdirection of each of through holes 421-424 are positioned to almostaccord with each other. The entire range of the grooved area offlow-passage portion 22, in which the second groove 222 is formed, ispositioned within the area of flow-passage portion 42 of housing 4, inwhich through holes 421-424 are formed.

At the opposite position “B” (see FIG. 5), the volume of annular space βbecomes minimum. The end of the negative x-axis direction of flangedportion 211 is positioned to be slightly offset from the end of thenegative x-axis direction of the inward opening of oblique hole 412,which opens into the interior space of sliding-contact bore 40 throughthe inner peripheral surface of large-diameter bore 40 a, toward thepositive x-axis direction.

Depending on a change in the axial position of spool 20, arising from asliding motion of spool 20 in the x-axis direction, the volume ofannular space β changes (increases or decreases). Movement of air in andout of the annular space β, occurring as a result of the sliding motionof spool 20, can be smoothly achieved through the oblique hole 412, thusensuring a smooth operation (a smooth sliding motion) of spool 20.

(Opening and Closing Action of Spool Valve)

In the shown embodiment, a plurality of circumferentially-equidistantspaced through holes (four through holes 421-424) are formed in housing4. Additionally, annular groove 561 of unit mounting portion 56 isformed in a manner so as to surround the entire circumference of aportion of flow-passage portion 42 having through holes 421-424.Therefore, it is possible to more efficiently supply a large amount ofoil from the supply passage 53 a through the plurality of through holes421-424 to the spool 20. As previously discussed, in the shownembodiment, annular groove 561 is provided and formed in the engineblock EB and flow-passage portion 42 of housing 4 has four through holes421-424. In lieu thereof, annular groove 561 may be eliminated and alsoonly the first through hole 421, opposed to the supply passage 53 a inthe y-axis direction, may be formed (in other words, the other threethrough holes 422-424 may be eliminated).

Through holes 223-227 of spool 20 and through holes 421-424 of housing 4are configured such that fluid-communication between the first group ofthrough holes 223-226 and the second group of through holes 421-424 canbe established or blocked and that fluid-communication between throughhole 227 and the second group of through holes 421-424 can be blocked orestablished, depending on the axial position of spool 20, arising from asliding motion of spool 20 in the x-axis direction.

As viewed in the radial direction of housing 4, at an axial position ofspool 20 that the first groove 221 of spool 20 and the through holes421-424 overlap each other, for instance, at the position “A” (see FIG.4), annular space α1 is communicated with the through holes 421-424, andthus fluid-communication between the first group of through holes223-226 and the second group of through holes 421-424 is established.Hence, even when the first group of through holes 223-226 of the spoolside and the second group of through holes 421-424 of the housing sidedo not overlap each other in the circumferential direction owing torotary motion of spool 20 (flow-passage portion 22) about the axis “Q”with respect to the sliding-contact bore 40 (in other words, withrespect to the flow-passage portion 42 of spool valve body 4 a ofhousing 4), by virtue of the first groove 221 (in other words, annularspace α1), fluid-communication between the first group of through holes223-226 and the second group of through holes 421-424 cannot be blocked.Therefore, at the overlapping position of the first groove 221 andthrough holes 421-424, it is possible to reliably intercommunicate thefirst group of through holes 223-226 and the second group of throughholes 421-424, regardless of the presence or absence of rotary motion ofspool 20 about the axis “Q” with respect to the sliding-contact bore 40.Additionally, by the formation of the plurality of through holes 223-226and the plurality of through holes 421-424, it is possible to increasethe total opening area (i.e., the total flow passage area), thusenabling a large amount of oil to be more efficiently supplied from thesecond group of through holes 421-424 via the first group of throughholes 223-226 to the inner peripheral side of spool 20. Instead offorming the first groove 221 in the flow-passage portion 22 of spool 20,the number and shape of through holes 223-226 and/or the number of shapeof through holes 421-424 may be properly modified, such that, at leastat the position “A”, fluid-communication between the first group ofthrough holes 223-226 and the second group of through holes 421-424 canbe established even if spool 20 is positioned in any rotation positionwith respect to sliding-contact bore 40.

By the way, the second group of through holes 421-424 alwayscommunicates the annular groove 561 of unit mounting portion 56. Hence,at the overlapping position of the first groove 221 and through holes421-424, the first group of through holes 223-226 can be communicatedwith the supply passage 53 a, which opens into the annular groove 561.The inner peripheral side (the first pressure chamber) of flow-passageportion 22, into which the through holes 223-226 open, alwayscommunicates the supply passage 53 b via the through hole 420 of housing4. Thus, at the overlapping position at which the first groove 221 ofspool 20 and the through holes 421-424 overlap each other, supplypassage 53 a can be communicated with supply passage 53 b via thethrough holes 223-226. That is, at the overlapping position, the firstgroup of through holes 223-226 serves as a first communication passageintercommunicating supply passages 53 a and 53 b. The first group ofthrough holes 223-226 is a large flow control section whose opening areais greater than that of through hole 227 and through which a largeamount of fluid flow can be distributed.

In contrast, at a non-overlapping position at which the first groove 221and the through holes 421-424 do not overlap each other, for instance,at the opposite position “B” (see FIG. 5), annular space α1 is notcommunicated with the through holes 421-424, and thus there is nofluid-communication between the first group of through holes 223-226 andthe second group of through holes 421-424. As a result,fluid-communication between supply passages 53 a and 53 b via thethrough holes 223-226 is blocked. That is, at the opposite position “B”of FIG. 5, the opening of the large flow control section is closed andthus the first communication passage (through holes 223-226) is kept innon-communicated state.

As viewed in the radial direction of housing 4, an area of the firstgroove 221, which opens into the through holes 421-424, in other words,a flow-passage area that annular space α1 is communicated with thethrough holes 421-424 becomes maximum at the position “A”. Roughlyspeaking, the flow-passage area tends to gradually reduce, as the spool20 moves (slides) in the negative x-axis direction from the position“A”, in other words, as the annular space α1 moves in the negativex-axis direction with respect to the through holes 421-424. Moreconcretely, immediately after a first intermediate position “A1” ofspool 20 has been reached with spool 20 sliding in the negative x-axisdirection from the position “A”, the flow-passage area becomes less thanthe total opening area of through holes 223-226, which open into thefirst groove 221, in other words, a flow-passage area that the annularspace α1 always communicates the through holes 223-226. Thereafter, froma second intermediate position “B1” of spool 20 immediately before theopposite position “B”, the flow-passage area becomes zero. Within arange of sliding motion of spool 20 between the second intermediateposition “B1” and the opposite position “B”, the flow-passage arearemains kept at zero.

Hence, regarding the flow passage by way of the first communicationpassage (through holes 223-226), within a range of sliding motion ofspool 20 between the position “A” and the second intermediate position“B1”, fluid-communication between two supply passages 53 a-53 b can beestablished. Conversely, within a range of sliding motion of spool 20between the second intermediate position “B1” and the opposite position“B” (because of zero-overlapping of the first group of through holes223-226 and the second group of through holes 421-424),fluid-communication between two supply passages 53 a-53 b can beblocked. Within a range of sliding motion of spool 20 from the firstintermediate position “A1” to the second intermediate position “B1”, theflow-passage area by way of the first communication passage (throughholes 223-226) tends to gradually reduce (because of gradual overlappingof the first group of through holes 223-226 and the second group ofthrough holes 421-424), as the spool 20 moves in the negative x-axisdirection from the first intermediate position “A1”.

In this manner, by an axial displacement of spool 20, it is possible toperform switching between the open state and the closed state of thelarge flow control section, in other words, switching between theestablished (enabled) state and the blocked (disabled) state offluid-communication between two supply passages 53 a-53 b by way of thefirst communication passage (through holes 223-226).

In a similar manner, as viewed in the radial direction of housing 4, atan axial position of spool 20 that the second groove 222 of spool 20 andthe through holes 421-424 overlap each other, for instance, at theposition “B” (see FIG. 5), annular space a2 is communicated with thethrough holes 421-424, and thus fluid-communication between the throughhole 227 and the second group of through holes 421-424 is established.Hence, even when the through hole 227 of the spool side and the secondgroup of through holes 421-424 of the housing side do not overlap eachother in the circumferential direction owing to rotary motion of spool20 (flow-passage portion 22) about the axis “Q” with respect to thesliding-contact bore 40 (in other words, with respect to theflow-passage portion 42 of spool valve body 4 a of housing 4), by virtueof the second groove 222 (in other words, annular space a2),fluid-communication between the through hole 227 and the second group ofthrough holes 421-424 cannot be blocked. Therefore, at the overlappingposition of the second groove 222 and through holes 421-424, it ispossible to reliably intercommunicate the through hole 227 and thesecond group of through holes 421-424, regardless of the presence orabsence of rotary motion of spool 20 about the axis “Q” with respect tothe sliding-contact bore 40.

At the overlapping position of the second groove 222 and through holes421-424, the through hole 227 communicates the supply passage 53 a, andalso the inner peripheral side (the first pressure chamber) offlow-passage portion 22, into which the through hole 227 opens, alwayscommunicates the supply passage 53 b via the through hole 420 of housing4. Thus, at the overlapping position at which the second groove 222 ofspool 20 and the through holes 421-424 overlap each other, supplypassage 53 a can be communicated with supply passage 53 b via thethrough hole 227. That is, at the overlapping position, the through hole227 serves as a second communication passage intercommunicating supplypassages 53 a and 53 b. The through hole 227 is a small flow controlsection whose opening area is less than that of the first group ofthrough holes 223-226 and through which a small amount of fluid flow canbe distributed.

In contrast, at a non-overlapping position at which the second groove222 and the through holes 421-424 do not overlap each other, forinstance, at the position “A” (see FIG. 4), annular space a2 is notcommunicated with the through holes 421-424, and thus there is nofluid-communication between the through hole 227 and the second group ofthrough holes 421-424. As a result, fluid-communication between supplypassages 53 a and 53 h via the through hole 227 is blocked. That is, atthe position “A” of FIG. 4, the opening of the small flow controlsection is closed and thus the second communication passage (throughhole 227) is kept in its non-communicated state.

As viewed in the radial direction of housing 4, an area of the secondgroove 222, which opens into the through holes 421-424, in other words,a flow-passage area that annular space α2 is communicated with thethrough holes 421-424 becomes zero at the position “A”. Roughlyspeaking, the flow-passage area tends to gradually increase, as thespool 20 (i.e., annular space α2) moves (slides) in the negative x-axisdirection from the position “A”. More concretely, immediately after athird intermediate position “A0” of spool 20 has been reached with spool20 sliding in the negative x-axis direction from the position “A”, theflow-passage area becomes greater than zero. Thereafter, theflow-passage area remains kept at a value greater than zero, until theopposite position “B” has been reached.

Hence, regarding the flow passage by way of the second communicationpassage (through hole 227), within a range of sliding motion of spool 20between the position “A” and the third intermediate position “A0”(because of zero-overlapping of the through hole 227 (the second groove222) and the second group of through holes 421-424), fluid-communicationbetween two supply passages 53 a-53 b can be blocked. Conversely, withina range of sliding motion of spool 20 between the third intermediateposition “A0” and the opposite position “B”, fluid-communication betweentwo supply passages 53 a-53 b can be established.

In this manner, by an axial displacement of spool 20, it is possible toperform switching between the open state and the closed state of thesmall flow control section, in other words, switching between theestablished (enabled) state and the blocked (disabled) state offluid-communication between two supply passages 53 a-53 b by way of thesecond communication passage (through hole 227).

By the way, a flow-passage area that the second group of through holes421-424 is communicated with the annular space α2 varies depending onthe axial displacement of spool 20 in the negative x-axis direction fromthe third intermediate position “A0”. The flow-passage area isconfigured to be greater than an area of the through hole 227, whichopens into the second groove 222, (i.e., a flow-passage area thatannular space α2 is communicated with the through hole 227). In otherwords, the flow-passage area of the oil flow path, directed from thesupply passage 53 a via the through hole 227 to the supply passage 53 b,becomes minimum at the through hole (orifice) 227, regardless of theaxial position of spool 20. That is, the oil flow is constricted bymeans of the through hole (orifice) 227.

As discussed above, regarding supply passage 53, its inlet (supplypassage 53 a) opens from the sliding-contact surface of sliding-contactbore 40 (flow-passage portion 42 of housing 4) in sliding-contact withspool 20, whereas its outlet (supply passage 53 b) opens from one axialend (i.e., the end of the negative x-axis direction) of sliding-contactbore 40. Additionally, the first communication passage (through holes223-226) and the second communication passage (through hole 227) areprovided on the side of the sliding-contact surface of spool 20 insliding-contact with sliding-contact bore 40. The first communicationpassage (through holes 223-226) and the second communication passage(through hole 227) are merged with each other by the axial passage(i.e., the first pressure chamber) formed along the axis “Q”, and thencommunicated with the outlet of supply passage 53, that is, thedownstream supply passage 53 b. Within a range of axial displacement(sliding motion) of spool 20 from the position “A” (see FIG. 4) to theopposite position “B” (see FIG. 5), the flow-passage area of the oilflow path, directed from the supply passage 53 a through the annulargroove 561, through holes 421-424 and through holes 223-227 to the innerperipheral side (the first pressure chamber) of flow-passage portion 22,becomes a maximum value (i.e., a summed value of the opening areas ofthrough holes 223-226) at the position “A”. Within a range of axialdisplacement (sliding motion) of spool 20 from the position “A” to thefirst intermediate position “A1”, the flow-passage area remains keptapproximately maximum. As the spool 20 shifts from the firstintermediate position “A1” to the second intermediate position “B1”, theflow-passage area gradually decreases with a change in opening area(orifice area) of through holes 223-226. Within a range of axialdisplacement (sliding motion) of spool 20 from the second intermediateposition “B1” to the opposite position “B”, the flow-passage areabecomes a minimum value, corresponding to the opening area of thethrough hole 227, by a maximum flow-constricting orifice action ofthrough hole 227.

Owing to the throttled (constricted) flow-passage area, the flow rate ofoil flowing to the downstream side (i.e., supply passage 53 b) tends todecrease. Assuming that the flow rate of oil, fed into the upstreamsupply passage 53 a, is constant, the flow rate of oil, fed into thebranch passage 54, tends to increase by the decreased flow rate of oilflowing to the downstream supply passage 53 b. At the position “A”, theflow rate of oil, fed from the supply passage 53 a via the spool valve 2to the supply passage 53 b, becomes maximum. In contrast, at theopposite position “B”, oil, fed from the supply passage 53 a via thespool valve 2 to the supply passage 53 b, is limited to oil, flowing viaonly the through hole (orifice) 227. Thus, at the opposite position “B”,the flow rate of oil, flowing through the downstream supply passage 53b, becomes minimum. That is, most of oil (except for oil flowing via thethrough hole 227 to the supply passage 53 b), fed from pump P intosupply passage 53 a, is delivered into the branch passage 54.

In this manner, control valve apparatus 1 is configured to controlswitching between the opening of the large flow control section (throughholes 223-226) whose opening area is comparatively great and the openingof the small flow control section (through hole 227) whose opening areais less than that of the large flow control section, depending on theposition of the valve element (spool 20). At least in a specified statewhere the opening of the large flow control section (through holes223-226) is fully opened with a maximum opening area (corresponding tothe position “A”), the small flow control section (through hole 227) isclosed. Concretely, in a first state (i.e., at the position “A” of FIG.4) corresponding to a maximum axial displacement of spool 20 in oneaxial direction, the first communication passage (through holes 223-226)is kept in its communicated state, whereas the second communicationpassage (through hole 227) is kept in its non-communicated state.Conversely, in a second state (i.e., at the opposite position “B” ofFIG. 5) corresponding to a maximum axial displacement of spool 20 in theother axial direction, the second communication passage (through hole227) is kept in its communicated state, whereas the first communicationpassage (through holes 223-226) is kept in its non-communicated state.

(Control System Configuration)

Control valve apparatus 1 is configured to selectively switch one of theposition “A” and the opposite position “B” to the other by an electricalsignal output from controller CU to pilot valve (electromagneticsolenoid valve) 3. That is, an axial displacement of spool 20 occursresponsively to a control signal input into the pilot valve 3, and thenswitching between a full fluid-communication state of supply passages 53a-53 b (i.e., the position “A” of FIG. 4) and a maximumflow-constriction state (i.e., the opposite position “B” of FIG. 5) ismade. In this manner, the flow rate of oil, fed into the downstreamsupply passage 53 b, can be adjusted or controlled responsively to acontrol signal from controller CU to pilot valve 3.

The hydraulic pressure in the first pressure chamber, acts on eachsurface of the sidewall surfaces of flow-passage portion 22 of spool 20,all facing in the negative x-axis direction, namely, on the firstpressure-receiving surface. This hydraulic pressure, acting on the firstpressure-receiving surface, creates a first force F1 that forces orbiases spool 20 in the positive x-axis direction. Conversely, thehydraulic pressure in the second pressure chamber, acts on each surfaceof the sidewall surfaces of back-pressure portion 21 of spool 20, allfacing in the positive x-axis direction, namely, on the secondpressure-receiving surface. This hydraulic pressure, acting on thesecond pressure-receiving surface, creates a second force F2 that forcesor biases spool 20 in the negative x-axis direction.

As previously discussed, the area D1 of the first pressure-receivingsurface is set to be less than the area D2 of the secondpressure-receiving surface, that is, D1<D2. For the same hydraulicpressure, acting on each of the first and second pressure-receivingsurfaces, the first force F1 is less than the second force F2. Hence,the sliding force, produced as a result of the force difference (F2−F1)between the second force F2 acting in the negative x-axis direction andcreated by hydraulic pressure on the second pressure-receiving surfaceof the area D2 and the first force F1 acting in the positive x-axisdirection and created by hydraulic pressure on the firstpressure-receiving surface of the area D1, acts on spool 20 so as toforce the spool 20 in the negative x-axis direction.

The hydraulic pressure in the first pressure chamber is approximatelyequal to the hydraulic pressure in supply passage 53 b. At least at theposition “A”, the hydraulic pressure in a portion of supply passage 53 adownstream of the branched point 530 and the hydraulic pressure insupply passage 53 b can be regarded as to be approximately equal to eachother. Thus, the hydraulic pressure in the first pressure chamber canalso be regarded as to be approximately equal to the hydraulic pressurein a portion of supply passage 53 a downstream of the branched point530.

When a signal “A” is outputted from controller CU to pilot valve 3, thepilot valve 3 operates to connect the second pressure chamber to the oilpan O/P (that is, to the atmosphere), thus realizing a state where thehydraulic pressure in supply passage 53 b acts on only the firstpressure-receiving surface. Hence, by the first force F1, spool 20 isforced in the positive x-axis direction (i.e., in a direction thatincreases the flow-passage area of the flow path between supply passages53 a-53 b). In this manner, the position “A” can be realized. Converselywhen a signal “B” is outputted from controller CU to pilot valve 3, thepilot valve 3 operates to connect a portion of supply passage 53 adownstream of the branched point 530 to the second pressure chamber,thus realizing a state where a hydraulic pressure approximately equal tothe hydraulic pressure in supply passage 53 b (or the hydraulic pressurein supply passage 53 a) acts on both the first and secondpressure-receiving surfaces. Hence, by a force corresponding to thedifference (F2−F1) between the second force F2 and the first force F1,spool 20 is forced in the negative x-axis direction (i.e., in adirection that decreases or throttles the flow-passage area of the flowpath between supply passages 53 a-53 b). In this manner, the position“B” can be realized.

More concretely, when a signal “A” (i.e., an OFF signal) is outputtedfrom controller CU to pilot valve 3, the solenoid 34 of pilot valve 3becomes de-energized. Thus, ball 31, which is forced in the negativey-axis direction by the spring force of spring 32, acts to blockfluid-communication between axial passage 301 and relay passage 302.Simultaneously, the sealing surface of armature 33 moves apart from thesealing surface formed in the opening of the negative y-axis directionof relay passage 304, and as a result fluid-communication between relaypassages 304-305 is established. Hence, oil in a portion of supplypassage 53 a downstream of the branched point 530 is not fed into thesecond pressure chamber. Also, oil in the second pressure chamber isdrained through the axial passage 442, relay passages 303-305, and theexhaust passage (not shown) to the oil pan O/P. Thus, the hydraulicpressure in the second pressure chamber drops to a pressure levelsubstantially corresponding to atmospheric pressure. Owing to thehydraulic pressure acting on the second pressure-receiving surface,remarkably less than the hydraulic pressure acting on the firstpressure-receiving surface, the first force F1 becomes greater than thesecond force F2. As a result of this, spool 20 is forced in the positivex-axis direction, thus realizing the position “A”.

In contrast, when a signal “B” (i.e., an ON signal) is outputted fromcontroller CU to pilot valve 3, the solenoid 34 of pilot valve 3 becomesenergized. Thus, armature 33 moves in the positive y-axis directionagainst the spring force of spring 32 by a magnetic force. Hence, ball31 moves apart from the opening of the positive y-axis direction ofrelay passage 302, and as a result fluid-communication between axialpassage 301 and relay passage 302 is established. Simultaneously, thesealing surface of armature 33 is brought into abutted-engagement withthe sealing surface formed in the opening of the negative y-axisdirection of relay passage 304, and as a result fluid-communicationbetween relay passages 304-305 is blocked. Hence, oil in a portion ofsupply passage 53 a downstream of the branched point 530 is fed into thesecond pressure chamber through radial passage 443, axial passage 301,relay passage 303 and axial passage 442. Also, oil in the secondpressure chamber is not drained through the relay passages (e.g., relaypassage 304) to the oil pan O/P. Thus, the hydraulic pressure in thesecond pressure chamber becomes approximately equal to the hydraulicpressure in a portion of supply passage 53 a downstream of the branchedpoint 530. Owing to the hydraulic pressures acting on the first andsecond pressure-receiving surfaces, approximately equal to each other,the second force F2 becomes greater than the first force F1. As a resultof this, spool 20 is forced in the negative x-axis direction, thusrealizing the opposite position “B”.

In the embodiment, the signal “A” inputted to pilot valve 3 is an OFF(de-energization) signal, whereas the signal “B” inputted to pilot valve3 is an ON (energization) signal. The control valve apparatus of theembodiment is configured so that the axial position of spool 20 can beselectively shifted from one of two different positions (namely, theposition “A” and the opposite position “B”) to the other.

Controller CU carries out switching action between the signal “A” (anOFF signal of solenoid 34) and the signal “B” (an ON signal of solenoid34) appropriately depending on latest up-to-date information about theengine operating condition (e.g., the current engine load and thecurrent valve-timing control state). Hereby, the throttled (constricted)state of the flow path, through which supply passages 53 a-53 b arecommunicated with each other, can be adjusted, and thus the flow rate ofoil flowing through the supply passage 53 b and the flow rate of oilflowing through the branch passage 54 can be controlled.

OPERATION AND EFFECTS OF EMBODIMENT

(Effects Obtained by Electronic Control)

In the shown embodiment, control valve apparatus 1 is electronicallycontrolled in response to an electric signal (an electronic signal).That is, by outputting a selected one of signals “A” and “B” fromcontroller CU to pilot valve 3, the axial position of spool 20 (a valveelement) of control valve apparatus 1 can be electronically controlledfrom one of the position “A” (i.e., a full fluid-communication state)and the opposite position “B” (i.e., a maximum flow-constriction state)to the other with a high responsiveness, only as needed.

As a modification, a spring-offset, external-pilot-pressure operatedtype may be adopted as the control valve apparatus 1. For instance, oneaxial end of the spool is permanently biased in the positive x-axisdirection by a biasing member (e.g., a coiled spring), whereas theopposite end of the spool is forced in the negative x-axis direction bya hydraulic pressure in the supply passage, in other words, an externalpilot pressure. In such a spring-offset, external-pilot-pressureoperated type, the spool valve can be opened or closed depending on thehydraulic pressure in the supply passage. However, the spring-offset,external-pilot-pressure operated type has difficulty in arbitrarilyvarying a flow rate of lubricating oil flow into the downstream supplypassage (toward each of lubricated engine parts) and a flow rate ofworking oil flow into the upstream supply passage (toward the VTCdevice). The spring-offset, external-pilot-pressure operated spool valvetype is inferior to the electronically-controlled spool valve type, incontrollability.

In the case of the electronically-controlled type control valveapparatus 1 of the embodiment, it is possible to optimally control afluid-communication state of the flow path between supply passages 53a-53 b (in other words, both a supply flow rate of lubricating oil toeach of lubricated engine parts and a supply flow rate of working oil tothe VTC device) through all engine operating conditions as well asduring an engine startup.

By the way, in the embodiment, control valve apparatus 1 is operated byway of two-position control, in other words, ON/OFF control, that is,switching between the position “A” (a large opening degree of the flowpath between supply passages 53 a-53 b via spool valve 2) and theopposite position “B” (a small opening degree of the flow path betweensupply passages 53 a-53 b via spool valve 2). As compared to acontinuously variable solenoid-operated control valve system in whichthe axial position of the spool (in other words, the opening degree ofthe flow path between supply passages 53 a-53 b) can be continuouslyvaried, depending on a duty cycle of a pulse-width modulated signal ofenergization of the solenoid, control valve apparatus 1 of theembodiment, which is operated by way of two-position control, issuperior with respect to simplified and downsized control valve systemconfiguration.

In the embodiment, switching between the position “A” and the oppositeposition “B” of spool valve 2 is performed by ON-OFF control(energization/de-energization control) for the solenoid 34 of pilotvalve 3. In this manner, the opening degree of pilot valve 3 (i.e., theposition of armature 33) can be varied directly by solenoid 34. In lieuthereof, the ON/OFF controlled spool valve system may be replaced by acontinuously variable solenoid-operated control valve system in whichthe axial position of the spool (in other words, the opening degree ofthe flow path between supply passages 53 a-53 b) can be continuouslyvaried, depending on a duty cycle of a pulse-width modulated signal ofenergization of the solenoid. The duty-ratio-controlled continuouslyvariable solenoid-operated control valve system is superior with respectto reduced whole size of the spool valve system, but inferior withrespect to simplified control valve system configuration. Also, in theembodiment, sliding motion of spool 20 can be controlled by a controlpressure (a pilot pressure) created by pilot valve 3 and applied to theback-pressure chamber (i.e., the second pressure-receiving surface) ofspool valve 2. In lieu thereof, the spool may be operated directly by amagnetic force of a solenoid, that is, the pilot-operated spool valvemay be replaced by a solenoid-operated spool valve. Thesolenoid-operated spool valve is superior with respect to a higherresponsiveness, but inferior with respect to reduced whole size of thespool valve system.

(Optimization of Engine Lubricating Action and VTC Operability)

Controller CU is configured to output the signal “A” during high engineload operation that requires a high lubricating-oil flow rate and a highhydraulic pressure for engine lubrication, so that spool 20 iscontrolled to the position “A”. For instance, to determine whether theengine load is high or low, the processor of controller CU can useinformation from the crank angle sensor. With control valve apparatus 1controlled to the position “A”, the flow path between supply passages 53a-53 b is kept fully open but not throttled. Thus, lubricating oil of alarge flow rate and a high hydraulic pressure can be fed into supplypassage 53 b (toward each of lubricated engine parts). Each oflubricated engine parts can be smoothly operated depending on engineload.

Under a high engine-load state, the engine speed often becomes high, andthus the hydraulic pressure, supplied from pump P to supply passage 53a, also becomes high. Hence, even with the flow path controlled to thefully-open state, a sufficient amount of oil can be also supplied to thebranch passage 54 (toward the VTC device).

Controller CU is further configured to output the signal “B” when arapid operation of the VTC device (i.e., a high responsiveness of valvetiming control) is required for a superior operability of the VTCdevice, so that spool 20 is controlled to the opposite position “B”.With control valve apparatus 1 controlled to the opposite position “B”,the flow path between supply passages 53 a-53 b is throttled. The flowrate of lubricating oil fed to supply passage 53 b (toward each oflubricated engine parts) is limited, and therefore most of the oil,discharged and force-fed from pump P to supply passage 53 a, is fed intobranch passage 54 (toward the VTC device). Thus, high-pressure workingoil can be preferentially fed into the VTC device. Even under theabove-mentioned fully-throttled state (i.e., the maximumflow-constriction state), oil can be fed via only the through hole 227formed in spool 20 to supply passage 53 b (toward lubricated engineparts). The flow rate of oil, flowing via only the through hole 227 tosupply passage 53 b, is set to a flow rate equal to or slightly greaterthan a minimum flow rate needed to lubricate moving engine parts.

By the way, controller CU is further configured to output the signal “A”to the pilot valve 3 for a predetermined time delay (a set time of adelay timer incorporated in controller CU) after the engine has beenstarted. Thus, the position “A” of spool valve 2 is realized, and thus aflow rate of oil flowing through the supply passage 53 b can beincreased so as to preferentially feed most of oil, discharged andforce-fed from pump P to supply passage 53 a, into supply passage 53 b(i.e., toward lubricated engine parts), and simultaneously to limit oilsupply to the hydraulic actuator (the VTC device). Hereby, it ispossible to enhance a lubrication performance when restarting the engineafter the vehicle (the engine) was left for a long time in the enginestopped state, and also to suppress a stability of operation and astartability of the VTC device from deteriorating owing to oil includinga lot of air bubbles and fed to the VTC device immediately after anengine startup.

In this manner, in the embodiment, switching between the signal “A” andthe signal “B” is made depending on the engine operating condition(e.g., the current engine load and the current valve-timing controlstate). As a result of this, shifting of the axial position of spool 20between the position “A” and the opposite position “B”, in other words,switching of the flow path between supply passages 53 a-53 b from one ofa large opening degree of the flow path between supply passages 53 a-53b and a small opening degree of the flow path between supply passages 53a-53 b to the other is made, so as to optimally control a flow rate ofoil flow into the downstream supply passage (toward each of lubricatedengine parts) and a flow rate of oil flow into the upstream supplypassage (toward the VTC device). Thus, two requirements, namely, asuperior engine lubricating action and a superior VTC operability can beoptimally balanced to each other at a high level.

(Enhancement of Function of Flow-Rate Adjustment)

The apparatus as disclosed in JP57-173513 (hereinafter referred to as“first comparative example”) can also be applied to the same hydraulicsystem to which the control valve apparatus 1 of the embodiment can beapplied. In the apparatus as disclosed in the first comparative example,in order to realize the enhanced responsiveness of a hydraulic actuator,while suppressing an increase in capacity (an increase in discharge) ofan oil pump, when the discharge pressure of the oil pump is low and thusthe flow rate of oil fed into a supply passage is limited, the controlvalve apparatus is closed and as a result the flow rate of oil flowingthrough the supply passage downstream of the branched point is limitedto an amount of oil passing through a bypass passage (an orifice).Hereby, oil can be preferentially fed into the branch passage (towardthe hydraulic actuator). Conversely when the discharge pressure of theoil pump becomes high, the control valve apparatus is opened so as toincrease an amount of oil fed into each of lubricated engine parts.However, in the apparatus as disclosed in the first comparative example,there is a risk of the deterioration of a function of flow-rateadjustment. That is, the orifice of the apparatus as disclosed in thefirst comparative example is configured to open responsively to theinflow of oil into the orifice. Contaminants probably exist within theoil flowing into the orifice. There is an increased tendency for theorifice, whose opening area is small, to be choked by such contaminants(debris and/or dusts). Thus, there is a risk of deteriorating the oilsupply to the downstream side of the orifice (toward each of lubricatedengine parts).

More concretely, there is a possibility that debris, arising frommachining (drilling), still remains within the supply passage to beconnected to the control valve apparatus, at least before the first oilflow through the supply passage. Also, due to wear of each of movingengine parts during operation of the engine, dusts are produced. Thereis a risk that the opening of the orifice is choked due to the produceddusts and/or debris.

Also, when the oil was left for a long time under a state where there isno oil flow, that is, with zero oil-flow velocity, or with low oil-flowvelocity, in other words, with stagnant oil, oil clot, having a highviscosity, may be produced. Such oil clot often stays in the oilpassage. For instance, when the oil pump comes into operation and thusoil begins to flow into the oil passage, the oil clot, sticking in theoil passage, falls away from the inner peripheral wall of the oilpassage and then mixed with the circulating oil. Thus, there is a riskthat the opening of the orifice is choked due to the fallen oil clot.

By the way, generally, the opening area of the orifice is less than thearea of one mesh of a usual oil filter. In the case that such a usualoil filter is used, it is difficult to remove or purify almost all ofcontaminants (debris and dusts). It is difficult to certainly avoid theopening of the orifice from being choked due to the contaminants. Tocertainly remove contaminants, a contaminant-purifying filter must beinstalled separately from the usual oil filter. This leads to thedemerit of increased manufacturing costs.

In contrast to the above, control valve apparatus 1 of the embodiment isconfigured to control, depending on the axial position of the valveelement (spool 20), switching between the opening of the large flowcontrol section (through holes 223-226) whose maximum opening area iscomparatively large and the opening of the small flow control section(through hole 227) whose maximum opening area is comparatively small. Atleast in a specified state where the opening of the large flow controlsection is fully opened with a maximum opening area, the opening of thesmall flow control section (serving as an orifice) is closed.Concretely, at the position “A” of spool 20, the first communicationpassage (through holes 223-226) is kept in its communicated state andsimultaneously the opening of through hole 227, which opens from thebottom of second groove 222, is blocked by the root 426 of flow-passageportion 42 of housing 4 such that the second communication passage(through hole 227) is kept in its non-communicated state.

For the reasons discussed above, even when contaminants are mixed withthe oil, there is a less possibility the opening of the secondcommunication passage (through hole 227) may be choked due to thecontaminants, because of no distribution of oil through the small flowcontrol section (through hole 227) at least during the large flowcontrol with spool 20 held at the position “A”. Thus, it is possible toeffectively suppress the through hole 227 from being undesirably chokeddue to contaminants. Thereafter, when spool 20 has been shifted to theopposite position “B”, the small flow control cannot be prevented.

There is a slight tendency that contaminants stay in the opening ofthrough hole 227, which opens from the inner peripheral surface ofcylindrical bore 220 of flow-passage portion 22 of spool valve 2, due tooil flow within the first pressure chamber even during the large flowcontrol. In such a case, there is a less possibility that thecontaminants are press-fitted into the opening of through hole 227. Thisis because the opening of through hole 227, which opens from the bottomof second groove 222, is blocked by the root 426 of flow-passage portion42 of housing 4. Thereafter, when the flow control mode has beenswitched to the small flow control, the contaminants, sticking in theopening of through hole 227, can be easily pushed and swept away by oilflown out of the opposite opening of through hole 227, which opens fromthe bottom of second groove 222. Hence, there is no problem.

Therefore, during the small flow control (i.e., during the throttledcontrol) with spool 20 held at the opposite position “B”, it is possibleto feed a desired amount of oil into the downstream supply passage 53 bas well as the upstream supply passage 53 a. Hereby, it is possible toenhance the function of flow-rate adjustment of control valve apparatus1.

Suppose that the axial position of the valve element (spool 20) iscontinuously controlled within the entire range of axial stroke of spool20. This eliminates the necessity for opening the second communicationpassage (through hole 227), during the flow control with the firstcommunication passage (though holes 223-226) opened. From the viewpointof a reduction of contaminants staying in the opening of through hole227, it is preferable to maintain the opening of the secondcommunication passage (through hole 227) at its blocked state. Forinstance, suppose that the layout (the relative-position relationship)among the first group of through holes 223-226, the second group ofthrough holes 421-424, and the through hole 227 is preset such that thesecond communication passage (through hole 227) becomes kept in itsnon-communicated state within a stroke range (in the x-axis direction)in which the valve element (spool 20) is positioned with greaterfrequency during flow control according to a predetermined control logicfor reconciling an enhancement in lubrication performance and anenhancement in operability of the VTC device. The optimal setting of thelayout of the through holes can provide the same effect as discussedabove, that is, an enhancement in the function of flow-rate adjustment.

According to the shown embodiment, at least in a specified state wherethe large flow control section (through holes 223-226) is fully openedwith a maximum opening area, the small flow control section (throughhole 227) is closed. Concretely, at the position “A corresponding to amaximum axial displacement of spool 20 in the positive x-axis direction,the second communication passage (through hole 227) becomes kept in itsnon-communicated state.

Thus, according to the control valve apparatus of the embodiment inwhich the axial position of spool 20 can be selectively shifted (orswitched) between two different positions, namely, the position “A” andthe opposite position “B”, but, basically, spool 20 cannot be positionedat a certain intermediate position between these two positions “A” and“B”, the opening of through hole 227 is kept in its blocked state,except when selecting the opposite position “B”. In particular, duringthe large flow control that the position “A” is selected and thusthrough holes 223-226 are opened, the opening of through hole 227 isclosed (blocked). For this reason, it is possible to eliminate or avoida bad influence on the second communication passage (through hole 227)due to contaminants, thus enhancing the function of flow-rateadjustment.

Even assuming that the axial position of spool 20 continuouslycontrolled, it is possible to effectively suppress the secondcommunication passage (through hole 227) from being choked due tocontaminants, at least in a specified state where the opening of thelarge flow control section is fully opened with a maximum opening area(that is, at least during a time period during which spool 20 is kept inthe position “A”). In particular, in the case of adoption of a controllogic that spool 20 is controlled to the position “A” and thus theopening of the large flow control section is fully opened with a maximumopening area at least for the purpose of enhancing a lubricationperformance immediately after an engine startup, it is possible toeliminate or avoid a bad influence on the second communication passage(through hole 227) due to contaminants (oil clot), produced immediatelyafter an engine startup (an oil pump startup), as much as possible.

Even in the event that the through hole 227 has been choked due tocontaminants (oil clot), according to the shown embodiment in whichcontrol valve apparatus 1 can be electronically controlled in responseto an electric signal (an electronic signal), it is possible to providea fail-safe control function. For instance, during a signal output forcontrolling spool 20 to the opposite position “B”, controller CUreceives information from an oil pressure sensor, on whether an oilsupply to the downstream supply passage 53 b (toward each of lubricatedengine parts) is insufficient, and then determines, based on theinformation from the oil pressure sensor, whether the through hole 227is choked. When it is determined that the second communication passage(through hole 227) has been choked due to contaminants, controller CUexecutes a fail-safe flow control by which the first communicationpassage (through holes 223-226) is opened by moving the spool 20. Byvirtue of such a fail-safe flow control, the flow control of oil by wayof the second communication passage (through hole 227) is replaced withthe flow control of oil by way of the first communication passage(through holes 223-226). By way of the first communication passage, itis possible to certainly assume an appropriate flow rate of oil fed intothe downstream supply passage 53 b (toward each of lubricated engineparts).

(Operation and Effects Obtained by Flow Path Layout of One SupplyPassage Connected to Side Face of Spool and the Other Supply PassageConnected to Axial End of Spool)

In connecting supply passage 53 to spool 20, suppose that inlet andoutlet ports of spool valve 2, are provided on the same side face ofspool 20 in a manner so as to communicate the opening end of upstreamsupply passage 53 a and the opening end of downstream supply passage 53b, respectively, such that the opening degree (i.e., the flow-passagearea) of the flow path between supply passages 53 a-53 b can be adjusteddepending on the axial position (sliding motion) of spool 20. In thiscase, generally, the opening end of upstream supply passage 53 a and theopening end of downstream supply passage 53 b must be laid out to beaxially spaced from each other. This results in an increase in overallaxial length of spool valve 2. Alternatively, inlet and outlet ports ofspool valve 2, are provided on the same axial end of spool 20 in amanner so as to communicate the opening end of upstream supply passage53 a and the opening end of downstream supply passage 53 b,respectively, such that the opening degree (i.e., the flow-passage area)of the flow path between supply passages 53 a-53 b can be adjusteddepending on rotary motion of spool 20. In this case, generally, theopening end of upstream supply passage 53 a and the opening end ofdownstream supply passage 53 b must be laid out to be radially spacedfrom each other. This results in an increase in outside diameter ofspool valve 2.

In contrast to the above, in the embodiment, one of the two ports ofspool 20 is provided on the side of the sliding-contact surface of spool20 in a manner so as to communicate the opening end of upstream supplypassage 53 a, while the other port is provided on the axial end of spool20 in a manner so as to communicate the opening end of downstream supplypassage 53 b. Concretely, the inlet (i.e., supply passage 53 a) ofsupply passage 53 opens from the sliding-contact surface ofsliding-contact bore 40 (flow-passage portion 42 of housing 4) insliding-contact with spool 20, whereas the outlet (i.e., supply passage53 b) of supply passage 53 opens from one axial end (i.e., the end ofthe negative x-axis direction) of sliding-contact bore 40. Thiscontributes to the reduced radial dimension and reduced axial length ofspool valve 2. Thus, it is possible to compactify the whole size ofcontrol valve apparatus 1.

In the case of supply passage 53 (supply passages 53 a-53 b) of theshown embodiment, the direction (i.e., the y-axis direction) that theupstream supply passage 53 a extends and the direction (i.e., the x-axisdirection) that the downstream supply passage 53 b extends, differ fromeach other and intersect with each other at an approximately rightangle. In the shown embodiment, the control valve structure is designedso that spool 20 slides in the x-axis direction. In lieu thereof, thecontrol valve structure may be designed so that spool 20 slides in they-axis direction, and that the opening degree (i.e., the flow-passagearea) of the flow path between supply passages 53 a-53 b can be adjusteddepending on sliding motion of spool 20 in the y-axis direction.

Even with the above-discussed construction that the directions that theupstream and downstream supply passages 53 a-53 b extend, differ fromeach other and intersect with each other at an approximately rightangle, the provision of annular groove 561, formed to surround theentire circumference of the flow-passage portion, is advantageous withrespect to smooth oil flow from one port of spool valve 2 (i.e., supplypassage 53 a) to the other port (i.e., supply passage 53 b).

(Operation and Effects Obtained by Pressure-Receiving Surface AreaDifference D2−D1)

Generally, a sliding spool type control valve is superior from aviewpoint that its valve element (a spool) can be smoothly operated(moved) by a comparatively small force without being affected by ahydraulic pressure of fluid flowing through the spool valve, rather thancontrol valves of another type. Thus, the spool type control valve issuited to reliable control of flow for a high-pressure hydrauliccircuit.

However, in the control valve structure of the embodiment, a hydraulicpressure acts on each of axial ends of spool 20. For instance, supposethat spool 20 is operated directly by a magnetic force of a solenoid.Such an electromagnetic-solenoid-operated control valve system requiresa comparatively large magnetic force, overcoming the hydraulic pressure.This means an enlargement in the whole size of the solenoid-operatedcontrol valve system.

For the reasons discussed above, in the embodiment, pilot valve 3 isfurther provided and spool 20 is operated by applying a hydraulicpressure (a pilot pressure), concretely, a hydraulic pressure in supplypassage 53 a to the second pressure-receiving surface of spool 20 by wayof the pilot valve 3. In comparison with the solenoid-operated controlvalve system, the control valve apparatus 1 of the embodimentfacilitates switching of a high-pressure hydraulic circuit, concretely,smooth adjustment of flow of oil flowing through the flow path (i.e.,supply passage 53 b) downstream of the branched point 530, whilesuppressing the control valve system from being enlarged.

Also, in the embodiment, there is an area difference (D2−D1) between thesecond pressure-receiving surface of spool 20 and the firstpressure-receiving surface of spool 20. The control valve apparatus ofthe embodiment is configured to operate (shift) spool 20 by the forcedifference (F2−F1) of two opposite forces F2 and F1, acting onrespective axial ends of spool 20, which force difference is created bythe area difference (D2−D1). Hence, it is possible to reduce the size ofspool 20, while ensuring a smooth sliding motion (a high responsivenessof operation) of spool 20 laid out at a portion in which supply passages53 a-53 b intersect with each other at an approximately right angle.

Conversely, suppose that there is no area difference between the firstand second pressure-receiving surfaces and thus sliding motion of spool20 is created by the hydraulic pressure difference of hydraulicpressures acting on respective axial ends of spool 20. On the one hand,it is necessary to let the magnitudes of hydraulic pressures acting onrespective axial ends of spool 20 be different. Simultaneously, supposethat spool 20 is installed at a portion in which supply passages 53 a-53b intersect with each other at an approximately right angle. On theother hand, a hydraulic pressure the downstream end of supply passage(i.e., the downstream supply passage 53 b) always acts on the firstaxial end of spool 20 (i.e., the first pressure-receiving surface)during operation of the engine. For instance, assuming that spool 20 hasto be moved in the negative x-axis direction in which the first axialend of spool 20 faces, the magnitude of hydraulic pressure acting on thesecond axial end of spool 20 (i.e., the second pressure-receivingsurface) has to be increased than the magnitude of hydraulic pressureacting on the first axial end of spool 20 (i.e., the firstpressure-receiving surface). In this case, a hydraulic pressure in theupstream end of supply passage 53 (i.e., the upstream supply passage 53a) can be just used as a hydraulic pressure acting on the second axialend of spool 20 (i.e., the second pressure-receiving surface). However,a hydraulic pressure in the downstream end of supply passage 53 (i.e.,the downstream supply passage 53 b) to be used as a hydraulic pressureacting on the first axial end of spool 20 (i.e., the firstpressure-receiving surface) must be adjusted (dropped) by means of aflow-constriction device or a pressure control valve. This leads to theproblem of a pressure loss.

For the reasons discussed above, in order for spool 20 to move withoutproducing any pressure loss, the area difference (D2−D1) between thesecond pressure-receiving surface of the area D2 and the firstpressure-receiving surface of the area D1 is necessary.

Alternatively, suppose that there is no area difference between thefirst and second pressure-receiving surfaces and thus the forcedifference between forces acting on respective axial ends of spool 20 iscreated by the spring force of a biasing means (e.g., a spring-loadmeans). For instance, suppose that, to move the spool 20 in the negativex-axis direction, the spring force, produced by the biasing means, actson the second axial end of spool 20 (i.e., the second pressure-receivingsurface) instead of using the hydraulic pressure difference. In such acase, immediately after an engine startup there is a less development ofhydraulic pressure in supply passage 53, spool 20 can be held at theopposite position “B”, in which the flow path is conditioned in themaximum flow-constriction state of supply passages 53 a-53 b, by thespring force of the biasing means. Under these condition, when shiftingspool 20 from the opposite position “B” to the position “A”, there is alag time between (i) the point of time of switching from the signal “B”to the signal “A” and (ii) the point of time of a sufficient developmentof hydraulic pressure in supply passage 53, overcoming the spring forceof the biasing means. Thus, it is necessary to wait, until, thehydraulic pressure in supply passage 53 develops sufficiently. However,such a spring-offset type control valve system has difficulty inenhancing a lubrication performance by opening the flow path betweensupply passages 53 a-53 b during an engine startup. Spool 20 has to bemoved in the positive x-axis direction by the hydraulic pressure, whileovercoming the spring force of the biasing means during the enginestartup. There is a possibility that spool 20 cannot be operated(shifted) with a high responsiveness. Also, by the addition of thebiasing means (spring-load means), a working oil pressure range, withinwhich spool 20 can be operated, tends to become narrow, and as a resultit is difficult to ensure a smooth sliding motion (a high responsivenessof operation) of spool 20.

Conversely, suppose that, in order for spool 20 to move in the positivex-axis direction, the spring force, produced by the biasing means, actson the first axial end of spool 20 (i.e., the first pressure-receivingsurface) instead of using the hydraulic pressure difference. In such acase, immediately after an engine startup, spool 20 can be held at theposition “A”, in which the flow path is conditioned in the fullfluid-communication state of supply passages 53 a-53 b, by the springforce of the biasing means. Under these conditions, when shifting spool20 from the position “A” to the opposite position “B”, in other words,for switching to the maximum flow-constriction state of supply passages53 a-53 b, spool 20 has to be moved in the negative x-axis direction bya sufficient hydraulic pressure acting on the second axial end of spool20 (i.e., the second pressure-receiving surface), overcoming the springforce of the biasing means. To produce the sufficient hydraulicpressure, which acts on the second pressure-receiving surface, higherthan the hydraulic pressure, which acts on the first pressure-receivingsurface, the area difference between the second pressure-receivingsurface and the first pressure-receiving surface is necessary.

In contrast, in the embodiment, spool 20 can be operated by the forcedifference (F2−F1) of two opposite forces F2 and F1, acting onrespective axial ends of spool 20, which force difference is created bythe pressure-receiving surface area difference (D2−D1), without anybiasing means (e.g., without any spring-load means) acting on spool 20.

Thus, it is unnecessary to wait, until the hydraulic pressure in supplypassage 53 develops sufficiently. Even when hydraulic pressures actingrespective axial ends of spool 20 are still low, it is possible toproduce a force needed to axially move the spool 20 by virtue of thearea difference (D2−D1). A working oil pressure range, within whichspool 20 can be operated, is comparatively wide and also it isunnecessary to move the spool 20 against the spring force, because of noaddition of biasing means (spring-load means). Thus, it is possible toensure a smooth sliding motion (a high responsiveness of operation) ofspool 20. Therefore, at an early stage after the engine has beenstarted, switching of the flow path between a full fluid-communicationstate of supply passages 53 a-53 b (i.e., the large flow control modecorresponding to the position “A” of FIG. 4) and a maximumflow-constriction state (i.e., the small flow control mode correspondingto the opposite position “B” of FIG. 5) can be made with a highresponsiveness, and thus flow control can be rapidly accuratelyperformed.

Additionally, there is no biasing means (no sprang-load means) acting onspool 20, the number of component parts can be reduced. Also, only thehydraulic pressure acts on each of the first and secondpressure-receiving surfaces of spool 20, and additionally the magnitudeof hydraulic pressure acting on the first pressure-receiving surface andthe magnitude of hydraulic pressure acting on the secondpressure-receiving surface are approximately equal to each other. Hence,even in the case of a slight pressure-receiving surface area difference(D2−D1), it is possible to operate spool 20, utilizing the forcedifference (F2−F2) created by the slight pressure-receiving surface areadifference (D2−D1). As a result, spool valve 2 (especially, the radialsize of spool 20) can be downsized. In other words, control valveapparatus 1 of the embodiment can reconcile both the reduced size ofspool 20 and the same high responsiveness as the previously-discussedspring-offset type control valve system.

Furthermore, the hydraulic pressure in the downstream end of supplypassage 53 (i.e., the downstream supply passage 53 b) is just used as ahydraulic pressure acting on the first axial end of spool 20 (i.e., thefirst pressure-receiving surface), while the hydraulic pressure in theupstream end of supply passage 53 (i.e., the upstream supply passage 53a) is just used as a hydraulic pressure acting on the second axial endof spool 20 (i.e., the second pressure-receiving surface). Thus, thereis a less wasteful pressure loss.

In particular, control valve apparatus 1 of the embodiment is configuredto selectively introduce oil of the upstream side of supply passage 53(i.e., the upstream supply passage 53 a) into the second pressurechamber (the side of the second pressure-receiving surface) withoutintroducing oil of the downstream side of supply passage 53 (i.e., thedownstream supply passage 53 b) into the second pressure chamber. Ascompared to another type of control valve system in which oil of thedownstream side of supply passage 53 (i.e., the downstream supplypassage 53 b) is introduced into the second pressure chamber, in thecontrol valve apparatus 1 of the embodiment that selectively introducesoil of the upstream side of supply passage 53 (i.e., the upstream supplypassage 53 a) into the second pressure chamber, there is a less pressureloss of hydraulic pressure introduced into the second pressure chamber(the side of the second pressure-receiving surface). Hence, the pressuredifference between hydraulic pressure introduced into the secondpressure chamber and hydraulic pressure introduced into the firstpressure chamber tends to become less. As a result, spool 20 can beeffectively shifted by virtue of the area difference (D2−D1) between thearea D2 of the second pressure-receiving surface (the second axial endof spool 20) and the area D1 of the first pressure-receiving surface(the first axial end of spool 20), in other words, by the sliding force(i.e., F2−F1), produced as a result of the force difference between theaxial force F2 acting in the negative x-axis direction and created byhydraulic pressure on the second pressure-receiving surface of the areaD2 and the axial force F1 acting in the positive x-axis direction andcreated by hydraulic pressure on the first pressure-receiving surface ofthe area D1. Thus, it is possible to ensure a smooth sliding motion (ahigh responsiveness of operation) of spool 20.

(Operation and Effects Obtained by Flow Path Layout of Upstream SupplyPassage Connected to Side Face of Spool and Downstream Supply PassageConnected to Axial End of Spool)

In the embodiment, spool 20 is laid out to slide in the direction (i.e.,in the x-axis direction) that the downstream supply passage 53 bextends. In other words, the inlet port of spool 20 is provided on theside of the sliding-contact surface of spool 20 in a manner so as tocommunicate the opening end of upstream supply passage 53 a, while theoutlet port of spool 20 is provided on the axial end of spool 20 in amanner so as to communicate the opening end of downstream supply passage53 b.

Thus, the direction of flow of oil flowing via the inlet port of spool20 (i.e., the opening end of upstream supply passage 53 a) into spoolvalve 2 is substantially perpendicular to the direction of slidingmotion of spool 20. The direction of flow of oil flowing via the spoolinlet port into spool valve 2 is not the axial direction of spool 20.Thus, it is possible to suppress the operation (the sliding motion) ofspool 20 from being affected by dynamic pressure, which may be createdby the flow velocity of oil flowing through spool 20. In particular,even when the oil-flow velocity is high, it is possible to suppressunintended sliding motion of spool 20, thus enabling stable operation ofspool 20, that is, more accurate flow control.

Furthermore, annular groove 561 is provided to surround the entirecircumference of the flow-passage portion of spool valve 2, and thusoil, supplied from supply passage 53 a to spool valve 2, is necessarilydistributed into annular groove 561. This contributes to equalization ofthe supplied oil pressure, thus more certainly enabling stable operationof spool 20 and more accurate flow control.

Moreover, the inlet port of spool 20 (i.e., the opening end of upstreamsupply passage 53 a) is provided on the side of the sliding-contactsurface of spool 20 rather than on the axial end of spool 20. Thedistance between the opening end of upstream supply passage 53 a and thesecond axial end of spool 20 (i.e., the second pressure-receivingsurface) is shorter than the distance between both axial end faces ofspool 20. In the case of the embodiment in which the flow path isconfigured to selectively introduce oil of the upstream side of supplypassage 53 (i.e., the upstream supply passage 53 a) into the secondpressure chamber (the side of the second pressure-receiving surface), itis possible to simplify the flow-passage structure among the spool inletport, the opening end of upstream supply passage 53 a, and the secondpressure chamber. Concretely, the system of the embodiment does notrequire the addition of a hydraulic line interconnecting the upstreamsupply passage 53 a and the oil passage (i.e., radial passage 443)formed in pilot valve body 4 c. This is because seal retaining bore 562of engine block EB also serves as a hydraulic line interconnecting theupstream supply passage 53 a and the radial passage 443. Thiscontributes to smaller space requirements of overall system, reducedmanufacturing costs and simplified control valve apparatus.

Additionally, the length of the hydraulic line interconnecting theupstream supply passage 53 a (i.e., the inlet side of spool 20) and thesecond axial end of spool 20 (i.e., the second pressure-receivingsurface) can be shortened. This contributes to a less pressure loss ofoil, which is introduced from the former (supply passage 53 a) to thelatter (the second pressure-receiving surface), that is, a smoothsliding motion (a high responsiveness of operation) of spool 20.

(Operation and Effects Obtained by Layout of Pilot Valve)

Suppose that the centerline of pilot valve 3 is laid out in the x-axisdirection, for example, coaxially with the centerline of spool valve 2such that these centerlines pass through the axis “Q” of sliding motionof spool 20. In such a case, pilot valve 3 is located to protrude fromthe side face 100 of engine block EB in the positive x-axis direction,thus deteriorating the layout flexibility of control valve apparatus 1.Also, the distance between supply passage 53 and axial passage 301,which axial passage is formed in pilot valve 3 for intercommunicatingthe supply passage 53 and the second axial end of spool 20 (i.e., thesecond pressure-receiving surface), tends to become longer. Such acontrol valve structure requires the addition of a hydraulic line formedin housing 4 for interconnecting the supply passage 53 and the axialpassage 301.

In contrast, in the embodiment, the axis of pilot valve 3 is laid out inthe y-axis direction in such a manner as to extend parallel to the sideface 100 of engine block EB. Thus, it is possible to suppress controlvalve apparatus 1 from protruding from the side face 100, thus enhancingthe layout flexibility of control valve apparatus 1. Also, the axis ofpilot valve 3 is laid out close to the side face 100 of engine block BB,and thus it is possible to shorten the distance between axial passage301 and supply passage 53 (concretely, upstream supply passage 53 a,annular groove 561, and seal retaining bore 562, all formed in engineblock EB). Therefore, it as possible to simplify the flow-passagestructure interconnecting the axial passage 301 and the supply passage53. More concretely, as the hydraulic line interconnecting thesepassages 301 and 53, control valve apparatus 1 of the embodimentrequires only the radial passage 443 formed in pilot valve body 4 c ofhousing 4. This contributes to reduced manufacturing costs andsimplified, downsized control valve apparatus.

(Operation and Effects Obtained by a Valve Unit Formed by IntegratingTwo Valve Components)

As a valve unit with both the spool valve 2 and the pilot valve 3 (inother words, with all of spool 20, pilot valve 3, and housing 4, whichdefines therein the sliding-contact bore 40), control valve apparatus 1is easily assembled into the unit mounting portion 56 of engine blockEB. Such a valve unit contributes to lower hydraulic system installationtime and costs, reduced service time, and smaller space requirements ofoverall system.

(Operation and Effects Obtained by Flow-Constriction Orifice Structure)

The operation and effects, obtained by the flow-constriction orificestructure of control valve apparatus 1 of the embodiment is hereunderdescribed, while comparing with the apparatus of the second comparativeexample shown in FIG. 6.

Referring now to FIG. 6, there is shown a partial cross-section ofcontrol valve apparatus 1 of the second comparative example, in which aflow-constriction device, which is provided for throttling orconstricting the flow-passage area of the flow path between supplypassages 53 a-53 b, is constructed by the apertures defined between theinner peripheral surfaces of through holes 421-424 of housing 4 and oneaxial end of spool 20, instead of forming a through hole (radial throughhole 227) in the spool 20. The cross-section of FIG. 6 shows the partialcross-section passing through the centerline “Q” of control valveapparatus 1 of the second comparative example (that is, the axis ofsliding motion of spool 20), under a state of the maximum displacementof spool 20 in the negative x-axis direction.

As clearly shown in FIG. 6, in the second comparative example, spool 20does not have flow-passage portion 22. Spool 20 is formed into asubstantially cylindrical hollow shape, but closed at one axial end suchthat partition wall portion 23 constructs the bottom of spool 20. Theaxial length of spool 2 of the second comparative example is dimensionedto be shorter than that of the embodiment. Notice that spool 20 of thesecond comparative example does not have through holes 223-227.

Spool 20 has an intermediate stepped portion 213 formed integral withthe flanged portion 211 in such a manner as to extend from the side faceof flanged portion 211 in the negative x-axis direction by apredetermined axial length. Intermediate stepped portion 213 is formedinto an annular shape. The outside diameter of intermediate steppedportion 213 is dimensioned to be slightly less than that of flangedportion 211 and also dimensioned to be slightly greater than the insidediameter of small-diameter bore 40 b.

In a similar manner to the embodiment (see FIGS. 4-5), in the secondcomparative example (see FIG. 6), sliding motion of spool 20 in thepositive x-axis direction is restricted by abutment between the end faceof the positive x-axis direction of flanged portion 211 and the end faceof the negative x-axis direction of threaded plug 413. On the otherhand, sliding motion of spool 20 in the negative x-axis direction isrestricted by abutment between the end face of the negative x-axisdirection of intermediate stepped portion 213 and the leftmost end face(viewing FIG. 5) of flow-passage portion 42 of housing 4, facing in thepositive x-axis direction. That is, the end face of the negative x-axisdirection of intermediate stepped portion 213 and the leftmost end faceof flow-passage portion 42 of housing 4, facing in the positive x-axisdirection, cooperate with each other to provide a second stopper (asliding-motion stopper for spool 20 in the negative x-axis direction) bywhich the opposite restricted position “B” shown in FIG. 6 is realized.

Intermediate stepped portion 213 is formed to have its outside diameterslightly less than that of flanged portion 211. Even with the spool 20held at the position “B”, an annular space can be defined between theouter peripheral surface of intermediate stepped portion 213 and theinner peripheral surface of large-diameter bore 40 a (a large-diameterportion of sliding-contact bore 40). Thus, the inward opening of obliquehole 412, which opens into the interior space of sliding-contact bore 40through the inner peripheral surface of large-diameter bore 40 a, is notclosed but always open. This enables the smooth movement of air in andout of the annular space through the oblique hole 412 during slidingmotion of spool 20, thus ensuring a smooth operation (a smooth slidingmotion) of spool 20.

With spool 20 held at the position “A”, the end face of spool 20, facingin the negative x-axis direction, that is, the right-hand side face ofthe bottom 23 is positioned to close approximately one-half (theleft-hand half) of each of through holes 421-424 by the outsidecylindrical surface of spool 20. In other words, at the position “A”,each of through holes 421-424 is approximately half-opened. At thisrestricted position “A”, the opening degree of through holes 421-424becomes maximum, and thus the flow-passage area of the oil flow path,directed from the supply passage 53 a through the annular groove 561 andthrough holes 421-424 to the inner peripheral side of flow-passageportion 42 (supply passage 53 b), becomes a maximum value.

The opening area (the flow-passage area) of the through holes 421-424tends to gradually reduce (because of gradual overlapping of the outsidecylindrical surface of spool 20 and the through holes 421-424), as spool20 moves from the position “A” to the opposite position “B” in thenegative x-axis direction and thus the axial displacement of spool 20 inthe negative x-axis direction increases.

With spool 20 held at the opposite position “B” (see FIG. 6), the endface of spool 20, facing in the negative x-axis direction, that is, theright-hand side face of the bottom 23 is positioned to be slightlyoffset from the end of the negative x-axis direction of each of throughholes 421-424 toward the positive x-axis direction. In other words, atthe opposite position “B”, spool 20 and the through holes 421-424 offlow-passage portion 42 of housing 4 largely overlap each other. At thisrestricted position “B” (i.e., the largely overlapping position of FIG.6), the opening degree of through holes 421-424 becomes minimum, andthus the flow-passage area of the oil flow path, directed from thesupply passage 53 a through the annular groove 561 and through holes421-424 to the inner peripheral side of flow-passage portion 42 (supplypassage 53 b), becomes a minimum value.

As discussed above, in the second comparative example of FIG. 6, theapertures defined between the inner peripheral surfaces of through holes421-424 of housing 4 and the first axial end of spool 20, facing in thenegative x-axis direction, serve as a flow-constriction device (avariable orifice). When spool 20 is positioned at the opposite position“B” (see FIG. 6), the apertures (the variable orifice) provide a maximumflow-constricting orifice action. Also, at the opposite position “B”(see FIG. 6), corresponding to the maximum axial displacement of spool20 in the negative x-axis direction, the first axial end of spool 20,facing in the negative x-axis direction, exists within the through holes421-424, as viewed in the radial direction of housing 4. Moreconcretely, in the second comparative example of FIG. 6, at the position“A” as well as at the opposite position “B”, the first axial end ofspool 20, facing in the negative x-axis direction, exists within thethrough holes 421-424, as viewed in the radial direction of housing 4.That is, the first axial end of spool 20, facing in the negative x-axisdirection, is not supported by the entire inner periphery ofsmall-diameter bore 40 b.

The other construction of the second comparative example of FIG. 6 isexactly the same as the embodiment of FIGS. 4-5.

In contrast to the flow-path configuration of the embodiment (see FIGS.4-5) in which oil can be fed from annular groove 561 through the secondgroup of through holes 421-424 and the first group of through holes223-226 to the inner peripheral side of flow-passage portion 42 (supplypassage 53 b), according to the flow-path configuration of the secondcomparative example (see FIG. 6), oil is fed into the inner peripheralside of flow-passage portion 42 directly through the through holes421-424. Thus, it is easy to enlarge the flow-passage area of the oilflow path, directed from the supply passage 53 a through the annulargroove 561 and through holes 421-424 to the inner peripheral side offlow-passage portion 42 (supply passage 53 b), as compared to theflow-path configuration of the embodiment (see FIGS. 4-5). Hence, apressure loss of oil flowing through the control valve apparatus 1 canbe easily suppressed, thus enabling oil to be more rapidly fed to eachof lubricated engine parts, after the engine has been started.

In the shown embodiment of FIGS. 4-5, differing from the secondcomparative example of FIG. 6, through hole 227 is further formed in thegrooved portion of flow-passage portion 22 of spool 20 at which thesecond groove 222 is formed. Especially, at the opposite position “B”(see FIG. 5), through hole 227, bored in spool 20, serves as aflow-constriction orifice (an orifice) that throttles or constricts theflow-passage area of the flow path between supply passages 53 a-53 bwith a maximum flow-constricting orifice action. That is, spool 20 isformed with two kinds of holes, namely, the first communication hole (orthe first communication passage, concretely, through holes 223-226)whose opening area is large and the second communication hole (or thesecond communication passage, concretely, through hole 227) whoseopening area is small. When a flow rate of oil to be fed into supplypassage 53 b (toward each of lubricated engine parts) has to beincreased, the first communication passage is opened so as to feed oilto supply passage 53 b by way of the first communication passage.Conversely when a flow rate of oil to be fed into branch passage 54(toward the VTC device) has to be increased, the first communicationpassage is closed and simultaneously the second communication passage(the orifice) is opened so as to throttle the flow path between supplypassages 53 a-53 b. Instead of throttling the flow path between supplypassages 53 a-53 b by reducing the opening area of one kind of hole (seethe second comparative example of FIG. 6), control valve apparatus 1 ofthe embodiment uses two kinds of holes so as to throttle the flow pathbetween supply passages 53 a-53 b by switching from the closed state ofthe second communication hole (through hole 227) to the open state andby simultaneously switching from the open state of the firstcommunication hole (through holes 223-226) to the closed state. In thesecond comparative example of FIG. 6, in which, especially at theopposite position “B”, the flow-constriction device is constructed inthe form of a variable orifice (i.e., the apertures defined between theinner peripheral surfaces of through holes 421-424 of housing 4 and thefirst axial end of spool 20), utilizing the relative-positionrelationship between the axially sliding spool 20 and the stationaryspool valve body 4 a of housing 4, spool 20 (having back-pressureportion 21 but not having flow-passage portion 22) and spool valve body4 a (especially, through holes 421-424 formed in housing 4) both have tobe more accurately machined and produced. In contrast, the embodimentrequires accurate machining of only the through hole 227 (especially, anorifice bore of through hole 227 formed in spool 20), but not requirevery accurate machining of two different components, namely, spool 20and spool valve body 4 a of housing 4. That is, by accurate machining ofonly the orifice bore of through hole 227, it is possible to easilyrealize an accurate flow-passage area (i.e., an accurate orifice area)of the second communication passage, thus enabling the function offlow-rate adjustment to be enhanced, while largely suppressingindividual differences of flow-constriction orifices machined andmanufactured and also reducing manufacturing costs. That is, with spool20 shifted to the opposite position “B”, the flow rate of oil flowinginto the downstream supply passage 53 b can be more accuratelycontrolled or throttled by virtue of only the accurately-machinedorifice bore of through hole 227. Thus, it is possible to intendedlyrealize preferential feed of most of oil, discharged from pump P tosupply passage 53 a, into branch passage 54 (i.e., toward the VTCdevice) and distribution of a minimum amount of oil, needed forlubricating action, to each of lubricated engine parts.

Also, in the embodiment, spool 20 is supported at both sides of throughholes 421-424 of spool valve body 4 a of housing 4 within its entirestroke range from the position “A” to the opposite position “B”.Concretely, at the side of the positive x-axis direction of throughholes 421-424, spool 20 is supported by the entire inner periphery ofsliding-contact bore 40 (both large-diameter bore 40 a andsmall-diameter bore 40 b). Also, at the side of the negative x-axisdirection of through holes 421-424, spool 20 is supported by the entireinner periphery of sliding-contact bore 40 (small-diameter bore 40 b).Thus, it is possible to suppress the centerline of spool 20 from beingundesirably inclined with respect to the axis “Q” (i.e., the axis ofsliding motion of spool 20).

Suppose that spool 20 is supported at one side of through holes 421-424of spool valve body 4 a of housing 4 either at the side of the positivex-axis direction of through holes 421-424 or at the side of the negativex-axis direction of through holes 421-424. For instance, suppose that,only at the side of the positive x-axis direction of through holes421-424, spool 20 is supported by the inner periphery of sliding-contactbore 40 (see spool 20 of the second comparative example of FIG. 6 andhaving back-pressure portion 21 but not having flow-passage portion 22).In such a one-side support (see FIG. 6), the first axial end of spool20, facing in the negative x-axis direction, tends to be somewhatinclined toward the inside of each of through holes 421-424, in otherwords, in the radial direction. In contrast, in the both-side support ofthe embodiment shown in FIGS. 4-5, it is possible to suppress each axialend of spool 20 from being inclined in the radial direction. Thiscontributes to a smooth operation (a smooth sliding motion) of spool 20.

(Operation and Effects Obtained by Stopper)

In the embodiment, the inside diameter of the opening (i.e., throughhole 420) of the negative x-axis direction of flow-passage portion 42 ofhousing 4 is dimensioned to be less than that of small-diameter bore 40b (a small-diameter portion of sliding-contact bore 40 for spool 20), insuch a manner as to form the bottom 425 of the negative x-axis directionof flow-passage portion 42. The inside face of bottom 425 offlow-passage portion 42 of housing 4 cooperates with the end face of thenegative x-axis direction of spool 20 (flow-passage portion 22) toprovide a second stopper (a sliding-motion stopper for spool 20 in thenegative x-axis direction). This eliminates the necessity of providingor forming an additional stopper structure, thus ensuring reduced numberof component parts, lower machining time and costs, and compact controlvalve apparatus. Instead of using the second stopper, constructed by theend face of the negative x-axis direction of spool 20 and the insideface of bottom 425 of flow-passage portion 42 of housing 4, in a similarmanner to the second comparative example of FIG. 6, the spool 20 ofcontrol valve apparatus 1 of the embodiment may have an intermediatestepped portion 213 formed integral with the flanged portion 211 in amanner so as to construct the second stopper by the intermediate steppedportion 213 in cooperation with the leftmost end face of flow-passageportion 42 of housing 4, facing in the positive x-axis direction.

(Operation and Effects Obtained by Cylindrical Bore and Radial Groove)

In the embodiment, cylindrical bore (recessed portion) 210 is formed inthe back-pressure portion 21 of spool 20. This contributes to lighteningof spool 20 (that is, reduced inertial mass of the valve element), and asmooth sliding motion (a high responsiveness of operation) of spool 20,in other words, a rapid switching action between the position “A” andthe opposite position “B”. This also contributes to minimizing the areadifference (D2−D1) between the area D2 of the second pressure-receivingsurface (the second axial end of spool 20) and the area D1 of the firstpressure-receiving surface (the first axial end of spool 20), in otherwords, the sliding force (i.e., F2−F1), produced as a result of theforce difference between the axial force F2 acting in the negativex-axis direction and created by hydraulic pressure on the secondpressure-receiving surface of the area D2 and the axial force F1 actingin the positive x-axis direction and created by hydraulic pressure onthe first pressure-receiving surface of the area D1, as much aspossible.

Furthermore, it is possible to install a biasing member (e.g., a spring)within the internal space (i.e., the second pressure chamber) defined bycylindrical bore 210 of the back-pressure portion 21, thus ensuringexpanded design flexibility. For instance, suppose that an extensionspring is installed in the cylindrical bore 210 (in other words, thesecond pressure chamber) to permanently force the spool 20 in thepositive x-axis direction with respect to housing 4. The modificationcan provide the same operation and effects as a different modificationin which a coiled compression spring is installed in the first pressurechamber to permanently force the spool 20 in the positive x-axisdirection with respect to housing 4.

Conversely, suppose that the end face of spool 20, facing in thepositive x-axis direction, is not formed with cylindrical bore (recessedportion) 210, but formed as a flat end face (a closed flat face). When,with spool 20 held at the position “A”, spool 20 is further forced inthe positive x-axis direction by the hydraulic pressure in the firstpressure chamber (supply passage 53), the flat end face of spool 20 andthe inside end face of threaded plug 413 may adhere to each other with aless aperture between them. In such a case, it is difficult to deliveroil via pilot valve 3 through the flat end face of spool 20, facing inthe positive x-axis direction to the second pressure-receiving surface(i.e., the second pressure chamber).

In contrast, in the embodiment, the end face of spool 20, facing in thepositive x-axis direction, is formed with the cylindrical bore (recessedportion) 210. Thus, it is possible to suppress the end face of thepositive x-axis direction of spool 20 and the inside end face ofthreaded plug 413 from adhering to each other. Even with the flangedportion 211 of spool 20 kept in wall-contact with the inside end face ofthreaded plug 413, cylindrical bore (recessed portion) 210 facilitatesaxial movement of the flanged portion 211 apart from the threaded plug413 when delivering oil to the wall-contact portion. That is, when oilis fed via pilot valve 3 to the second axial end of spool 20 held at theposition “A”, it is possible to easily catch or receive oil introducedvia pilot valve 3 to the side of the second pressure-receiving surfaceby the cylindrical bore (recessed portion) 210. This enables a rapidsliding motion of spool 20 in the negative x-axis direction by rapidlygenerating a large magnitude of the second force F2, created byhydraulic pressure acting on the second pressure-receiving surface ofthe area D2.

By the way, when oil is fed via pilot valve 3 to the second pressurechamber of spool 20 held at the position “A”, first of all, oilintroduced from axial passage 442 of pilot valve body 4 c is fed intoannular groove 411 formed in the inner periphery of sliding-contact bore40 (large-diameter bore 40 a). Hence, oil can be fed into thecylindrical bore (recessed portion) 210, while being distributed aroundthe entire circumference of spool 20, thus ensuring more smoothintroduction of oil into the second pressure chamber. In this manner,annular groove 411 contributes to a rapid sliding motion of spool 20from the position “A” to the opposite position “B” (i.e., in thenegative x-axis direction).

Additionally, in the embodiment, the end face of the positive x-axisdirection of flanged portion 211 is formed with the radial groove 214.When spool 20 is positioned at the position “A”, oil can be deliveredfrom annular groove 411 via radial groove 214 to the cylindrical bore(recessed portion) 210. This ensures smooth oil supply to the secondpressure-receiving surface (the second pressure chamber), therebyfurther enhancing the above-mentioned effects obtained by the formationof cylindrical bore (recessed portion) 210.

Even when the angular position of radial groove 214 is arbitrarilychanged owing to rotary motion of spool 20 (back-pressure portion 21)about the axis “Q” with respect to the sliding-contact bore 40, oil canbe delivered by way of annular groove 411 via radial groove 214 to thecylindrical bore (recessed portion) 210.

Suppose that spool 20 is formed with only the radial groove 214 but notformed with the cylindrical bore (recessed portion) 210. The end face ofspool 20, facing in the positive x-axis direction, can receive hydraulicpressure only within an area corresponding to radial groove 214, untilmovement of the flanged portion 211 out of abutted-engagement with thethreaded plug 413 occurs. In contrast, in the embodiment, spool 20 isformed with the cylindrical bore (recessed portion) 210 as well as theradial groove 214, thus enabling the increased pressure-receivingsurface even when the flanged portion 211 is in abutted-engagement withthe threaded plug 413.

In the shown embodiment, although the flanged portion 211 has one radialgroove 214, it will be appreciated that the number of a radial groove isnot limited to “1”. The shape and the number of a radial groove formedin the flanged portion may be modified. Instead of forming the radialgroove 214 in the flanged portion 211 of spool 20, a communicationgroove, intercommunicating the annular groove 411 and the cylindricalbore (recessed portion) 210, may be formed in the threaded plug 413.Instead of forming a communication groove (i.e., radial groove 214),intercommunicating the annular groove 411 and the cylindrical bore(recessed portion) 210, a ridged portion may be formed on either theflanged portion 211 or the threaded plug 413. When the flanged portion211 is brought into abutted-engagement with the threaded plug 413 at theposition “A”, an aperture (a communication passage) can be definedbetween them by the ridged portion.

As will be appreciated from the above, control valve apparatus 1 of theembodiment can provide the following significant effects.

(1) In a hydraulic system equipped with a main flow passage (supplypassage 53) for feeding oil, discharged from an oil pump driven by aninternal combustion engine, to each of lubricated engine parts, a branchpassage 54 branched from the main flow passage at a branched point 530,and a hydraulic actuator (e.g., a VTC device) operated by a hydraulicpressure in the branch passage 54, the combination of:

a control valve apparatus 1 for adjusting a flow rate of the oil flowingthrough a portion (supply passage 53 b) of the main flow passagedownstream of the branched point 530, the control valve apparatus 1configured to control an opening of a large flow control section(through holes 223-226) and an opening of a small flow control section(through hole 227) whose opening area is less than that of the largeflow control section, depending on a position of a valve element (spool20), and

the control valve apparatus 1 further configured to close the opening ofthe small flow control section, at least in a specified state where theopening of the large flow control section is fully opened with a maximumopening area.

Thus, it is possible to enhance the function of flow-rate adjustment,while suppressing the opening of the small flow control section, whoseopening area is small, from being choked due to contaminants (debris anddusts).

The above-mentioned expression “adjustment of a flow rate of the oilflowing through a portion (supply passage 53 b) of the main flow passagedownstream of the branched point 530” is synonymous with “adjustment ofa flow rate of the oil flowing through the branch passage 54”. This isbecause the greater the flow rate of oil flowing through supply passage53 b that can be controlled by control valve apparatus 1, the smallerthe flow rate of oil flowing through branch passage 54, and vice versa.

Also, in the shown embodiment, although control valve apparatus 1 isapplied to the variable valve timing control (VTC) device serving as ahydraulic actuator, it will be appreciated that control valve apparatus1 may be applied to a hydraulic system with a hydraulic actuator ofanother type that requires a working pressure above a predeterminedpressure level. For instance, control valve apparatus 1 may be appliedto a hydraulic system with another type of hydraulically-operatedvariable valve operating device, such as a variable valve lift (VVL)system or a continuously variable valve event and lift control (VEL)system, or to a hydraulic system with a floating-bearing lubricationsystem (e.g., a turbine-bearing lubrication system of a turbocharger).

(2) The valve element (spool 20) is disposed in the portion (supplypassage 53 b) of the main flow passage downstream of the branched point530.

That is, in the embodiment, control valve apparatus 1 is disposed in themain flow passage (supply passage 53) downstream of the branched point530, for controlling or adjusting a flow rate of oil flowing through themain flow passage downstream of the branched point 530. In lieu thereof,control valve apparatus 1 may be disposed either in the branched point530 or in the branch passage 54, for flow-rate distribution between oildistributed to each of lubricated engine parts and oil distributed tothe hydraulic actuator. For instance, suppose that control valveapparatus 1 of a three-way type is disposed in the branched point 530,the downstream end of passage 54 is connected to each of lubricatedengine parts such that passage 54 serves as a main flow passage, and thedownstream end of passage 53 b is connected to the VTC device such thatpassage 53 b serves as a branch passage. In such a case, by throttlingthe opening degree of the three-way valve, a flow rate of oil flowingthrough the branch passage (passage 53 b) can be controlled to a smallflow-rate side. Conversely, by enlarging the opening degree of thethree-way valve, a flow rate of oil flowing through the branch passage(passage 53 b) can be controlled to a large flow-rate side. However,from the following viewpoints, the embodiment is superior to thismodification.

In the embodiment, as previously described, the valve element (spool 20)is disposed in the portion (supply passage 53 b) of the main flowpassage downstream of the branched point 530. In other situations,except for in the presence of a sufficient lubricating requirement, suchas during an engine startup in which lubricating action for movingengine parts is largely rapidly required, it is possible to throttle orcontrol the flow rate of oil distributed to each of lubricated engineparts to a minimum. Thus, it is possible to suppress oil, dischargedfrom the oil pump, from being wastefully exhausted, thus minimizingenergy loss. Additionally, by throttling or controlling the flow rate ofoil distributed to each of lubricated engine parts (to supply passage 53b) to a minimum value, needed for lubricating action, it is possible todistribute most of oil, discharged and force-fed from the oil pump,toward the hydraulic actuator (the VTC device) as much as possible. Theresponsiveness of the hydraulic actuator can be effectively enhanced.Control valve apparatus 1 of the embodiment uses a two-way valve. Thus,as compared to the use of a three-way valve having a more complicatedstructure, the two-way valve is simple, thus ensuring the increaseddesign flexibility.

In the embodiment, control valve apparatus 1 is constructed by thepilot-operated type two-way spool valve 2. That is, as a valve elementthat can control or adjust the valve opening depending on its axialposition, spool 20 is used. It will be appreciated that control valveapparatus 1 is not limited to such a pilot-operated type two-way spoolvalve. In lieu thereof, a control valve of another type may be used.That is, the spool valve may be replaced with another type, such as arotary valve, a needle valve, or a slide valve.

(3) Control valve apparatus 1 comprises a sliding-contact bore 40 intowhich an inlet (supply passage 53 a) of the main flow passage opens andfrom which an outlet (supply passage 53 b) of the main flow passageopens, and a spool 20 installed to axially move in the sliding-contactbore 40 only as needed, the sliding-contact bore 40 and the spool 20both disposed in the portion (supply passage 53 b) of the main flowpassage downstream of the branched point 530. The spool 20 has a firstcommunication passage (through holes 223-226) intercommunicating theinlet (supply passage 53 a) and the outlet (supply passage 53 b) and asecond communication passage (through hole 227) intercommunicating theinlet and the outlet and having an opening area less than an openingarea of the first communication passage. Control valve apparatus 1 isconfigured to bring the first communication passage to a communicatedstate and simultaneously to bring the second communication passage to anon-communicated state, in a first state where the spool 20 has movedwith a maximum displacement in one axial direction (i.e., the position“A” of FIG. 4) of the spool 20. Control valve apparatus 1 is furtherconfigured to bring the second communication passage to a communicatedstate and simultaneously to bring the first communication passage to anon-communicated state, in a second state where the spool 20 has movedwith a maximum displacement in the opposite axial direction (i.e., theposition “B” of FIG. 5) of the spool 20.

Thus, by the use of spool 20, it is possible to simply realize smoothswitching (smooth flow-rate adjustment) for a high-pressure hydrauliccircuit, through which, oil, discharged from the oil pump, flows.Additionally, in the maximum-displacement state of spool 20 (i.e.,either in the first state (the position “A”) or the second state (theopposite position “B”)), switching action of the first communicationpassage from one of the communicated state and the non-communicatedstate to the other and switching action of the second communicationpassage from one of the non-communicated state and the communicatedstate to the other can be simultaneously made. This contributes to thesimplified control system configuration. Furthermore, the secondcommunication passage, serving as the small flow control section (theflow-constriction orifice), is formed in the spool 20 in the form of athrough hole (hole 227). By accurate machining of only the secondcommunication passage (an orifice bore of through hole 227 formed inspool 20), it is possible to enhance the function of flow-rateadjustment.

(4) Control valve apparatus 1 comprises a sliding-contact bore 40 intowhich an inlet (supply passage 53 a) of the main flow passage opens andfrom which an outlet (supply passage 53 b) of the main flow passageopens, and a spool 20 installed to axially move in the sliding-contactbore 40 selectively between two opposite axial positions (the position“A” and the opposite position “B”) only as needed, the sliding-contactbore 40 and the spool 20 both disposed in the portion (supply passage 53b) of the main flow passage downstream of the branched point 530. Thespool 20 has a first communication passage (through holes 223-226)intercommunicating the inlet and the outlet and a second communicationpassage (through hole 227) intercommunicating the inlet and the outletand having an opening area less than an opening area of the firstcommunication passage Control valve apparatus 1 is configured to bringthe first communication passage to a communicated state andsimultaneously to bring the second communication passage to anon-communicated state, in a first state where the spool 20 has moved toone (the position “A”) of the two opposite axial positions. Controlvalve apparatus 1 is further configured to bring the secondcommunication passage to a communicated state and simultaneously tobring the first communication passage to a non-communicated state, in asecond state where the spool 20 has moved to the opposite axialdirection “B”.

This contributes to the simplified and downsized control valve systemconfiguration.

(5) The inlet (supply passage 53 a) of the main flow passage isconfigured to open from a sliding-contact surface of the sliding-contactbore 40 in sliding-contact with the spool 20, whereas the outlet (supplypassage 53 b) of the main flow passage is configured to open from afirst axial end of two opposite axial ends of the sliding-contact bore40. The first communication passage (through holes 223-226) and thesecond communication passage (through hole 227) are formed separatelyfrom each other in a sliding-contact surface of the spool 20 insliding-contact with the sliding-contact bore 40. The firstcommunication passage (through holes 223-226) and the secondcommunication passage (through hole 227) are configured to be mergedwith each other by an axial passage (the first pressure chamber) formedin the spool 20 along a centerline (the axis “Q”) of the spool 20, andthen communicated with the outlet (supply passage 53 b) of the main flowpassage.

Thus, it is possible to enhance the stability of operation (slidingmotion) of spool 20, while compactifying the whole size of control valveapparatus 1.

(6) The displacement of the spool 20 is electronically controlled.

Thus, it is possible to optimally control or adjust the flow rate of oildistributed to each of lubricated engine parts and the flow rate of oildistributed to the hydraulic actuator. Additionally, it is possible toensure an appropriate flow rate of oil fed toward each of lubricatedengine parts by a fail-safe flow control.

(7) The axial passage (the first pressure chamber) is configured to openfrom only the first axial end of two opposite axial ends of the spool20. A pressure-receiving surface area D2 of the second axial end(back-pressure portion 21) of the spool 20 is dimensioned to be greaterthan a pressure-receiving surface area D1 of the first axial end(flow-passage portion 22) formed with the axial passage (the firstpressure chamber). A hydraulic pressure in the main flow passage isselectively supplied or exhausted to or from the second axial end(back-pressure portion 21) of the spool 20 by an electromagnetic valve(pilot valve 3).

Thus, it is possible to reconcile the high responsiveness of operation(sliding motion) of spool 20 and the downsized spool 20.

(8) The second axial end (back-pressure portion 21) of the spool 20 hasa cylindrical bore (recessed portion 210) formed therein.

Thus, it is possible to realize light-weight and enhanced operability ofspool 20, thus reducing the whole size of control valve apparatus 1.

(9) The oil in the inlet (supply passage 53 a) of the main flow passageis introduced into the second axial end (back-pressure portion 21) ofthe spool 20.

Thus, it is possible to enhance the responsiveness of operation of spool20.

(10) The sliding-contact bore 40, the spool 20, and the electromagneticvalve are installed in the internal combustion engine in the form of avalve unit with the spool 20, the electromagnetic valve (pilot valve 3),and a housing 4, which defines therein the sliding-contact bore 40.

Thus, it is possible to realize lower hydraulic system installation timeand costs, reduced service time, and smaller space requirements ofoverall system.

The entire contents of Japanese Patent Application No. 2010-033193(filed Feb. 18, 2010) are incorporated herein by reference.

While the foregoing is a description of the preferred embodimentscarried out the invention, it will be understood that the invention isnot limited to the particular embodiments shown and described herein,but that various changes and modifications may be made without departingfrom the scope or spirit of this invention as defined by the followingclaims.

1. In a hydraulic system equipped with a main flow passage for feedingoil, discharged from an oil pump driven by an internal combustionengine, to each of lubricated engine parts, a branch passage branchedfrom the main flow passage at a branched point, and a hydraulic actuatoroperated by a hydraulic pressure in the branch passage, the combinationof: a control valve apparatus for adjusting a flow rate of the oilflowing through a portion of the main flow passage downstream of thebranched point, the control valve apparatus configured to control anopening of a large flow control section and an opening of a small flowcontrol section whose opening area is less than that of the large flowcontrol section, depending on a position of a valve element disposed inthe portion of the main flow passage downstream of the branched point,and the control valve apparatus further configured to close the openingof the small flow control section, at least in a specified state wherethe opening of the large flow control section is fully opened with amaximum opening area.
 2. In a hydraulic system equipped with a main flowpassage for feeding oil, discharged from an oil pump driven by aninternal combustion engine, to each of lubricated engine parts, a branchpassage branched from the main flow passage at a branched point, and ahydraulic actuator operated by a hydraulic pressure in the branchpassage, the combination of: a control valve apparatus for adjusting aflow rate of the oil flowing through a portion of the main flow passagedownstream of the branched point, the control valve apparatus comprisinga sliding-contact bore into which an inlet of the main flow passageopens and from which an outlet of the main flow passage opens, and aspool installed to axially move in the sliding-contact bore only asneeded, the sliding-contact bore and the spool both disposed in theportion of the main flow passage downstream of the branched point, andthe spool has a first communication passage intercommunicating the inletand the outlet and a second communication passage intercommunicating theinlet and the outlet and having an opening area less than an openingarea of the first communication passage, the control valve apparatusconfigured to bring the first communication passage to a communicatedstate and simultaneously to bring the second communication passage to anon-communicated state, in a first state where the spool has moved witha maximum displacement in one axial direction of the spool, and thecontrol valve apparatus further configured to bring the secondcommunication passage to a communicated state and simultaneously tobring the first communication passage to a non-communicated state, in asecond state where the spool has moved with a maximum displacement inthe opposite axial direction of the spool.
 3. The control valveapparatus as claimed in claim 2, wherein: the inlet of the main flowpassage is configured to open from a sliding-contact surface of thesliding-contact bore in sliding-contact with the spool, whereas theoutlet of the main flow passage is configured to open from a first axialend of two opposite axial ends of the sliding-contact bore, the firstand second communication passages are formed separately from each otherin a sliding-contact surface of the spool in sliding-contact with thesliding-contact bore, and the first and second communication passagesare configured to be merged with each other by an axial passage formedin the spool along a centerline of the spool, and then communicated withthe outlet of the main flow passage.
 4. The control valve apparatus asclaimed in claim 3, wherein: the displacement of the spool iselectronically controlled.
 5. The control valve apparatus as claimed inclaim 4, wherein: the axial passage is configured to open from only afirst axial and of two opposite axial ends of the spool, apressure-receiving surface area of the second axial end of the spool isdimensioned to be greater than a pressure-receiving surface area of thefirst axial end formed with the axial passage, and a hydraulic pressurein the main flow passage is selectively supplied or exhausted to or fromthe second axial end of the spool by an electromagnetic valve.
 6. Thecontrol valve apparatus as claimed in claim 5, wherein: the second axialend of the spool has a cylindrical bore formed therein.
 7. The controlvalve apparatus as claimed in claim 5, wherein: the oil in the inlet ofthe main flow passage is introduced into the second axial end of thespool.
 8. The control valve apparatus as claimed in claim 5, wherein:the sliding-contact bore, the spool, and the electromagnetic valve areinstalled in the internal combustion engine in the form of a valve unitwith the spool, the electromagnetic valve, and a housing, which definestherein the sliding-contact bore.
 9. The control valve apparatus asclaimed in claim 3, wherein: the first axial end of the sliding-contactbore, from which the outlet of the main flow passage opens, is formedwith a through hole whose inside diameter is dimensioned to be less thanan inside diameter of the sliding-contact bore in sliding-contact withthe spool to form a small-diameter bottom, and the small-diameter bottomconstructs a stopper that restricts the maximum displacement of thespool in the opposite axial direction.
 10. In a hydraulic systemequipped with a main flow passage for feeding oil, discharged from anoil pump driven by an internal combustion engine, to each of lubricatedengine parts, a branch passage branched from the main flow passage at abranched point, and a hydraulic actuator operated by a hydraulicpressure in the branch passage, the combination of: a control valveapparatus for adjusting a flow rate of the oil flowing through a portionof the main flow passage downstream of the branched point, the controlvalve apparatus comprising a sliding-contact bore into which an inlet ofthe main flow passage opens and from which an outlet of the main flowpassage opens, and a spool installed to axially move in thesliding-contact bore selectively between two opposite axial positionsonly as needed, the sliding-contact bore and the spool both disposed inthe portion of the main flow passage downstream of the branched point,and the spool has a first communication passage intercommunicating theinlet and the outlet and a second communication passageintercommunicating the inlet and the outlet and having an opening arealess than an opening area of the first communication passage, thecontrol valve apparatus configured to bring the first communicationpassage to a communicated state and simultaneously to bring the secondcommunication passage to a non-communicated state, in a first statewhere the spool has moved to one of the two opposite axial positions,and the control valve apparatus further configured to bring the secondcommunication passage to a communicated state and simultaneously tobring the first communication passage to a non-communicated state, in asecond state where the spool has moved to the opposite axial position.